I will start off by saying it may sound biased reading about the benefits of replacing a toilet tank lid on a web site that makes its livlihood selling toilet tank lids. I urge you to do your own homework if you don't trust any of the information presented here. We sell toilet tank lids because we believe for many reasons it is the easiest and least expensive way to repair a toilet with a broken toilet tank lid.
Replacing a toilet yourself can be a very easy process when everthing goes perfectly. Presuming you have already been to the store, selected the proper toilet (10" vs 12" vs 14" rough-in) for your bathroom, and have transported it to your house in a vehicle, and then carried or carted it to your bathroom, possibly up or down stairs, we are now going to remove the old toilet. Depending on how long your toilet has been there, the water supply line valve needs to be turned off and hopefully hasn't corroded and is long enough or short enough to reach your new toilet. Hopefully your bolt caps haven't ever been peed on or they will need to be cleaned and then popped off. Remove the 2 or 4 bolts holding your toilet to the floor. These often corrode over time depending on their age and the environment they are in. If they are corroded you will need to replace them. Hopefully you checked before you went to the store and bought the correct length. Now that the toilet is free from the floor and water supply you can just lift it (usually 60-100 pounds depending on its age - older toilets were made out of more porcelain so they tend to be heavier, and newer ones are typically made more cheaply so they save money by using less porcelain) up and set it aside. Now presuming the people who lived there before didn't take a shortcut and tile around the toilet when they put in new tile, you can install your wax ring (or two wax rings if the flange in the floor wasn't replaced when the new tile was put in, I hope you got two just to be safe), you just set your wax rings in place, replace the original rusted bolts in the floor and set the toilet down over them. Secure it in place with the bolts, and re-attach your water line. Install the seat. If the toilet didn't come fully assembled, you can now attach the tank to the bowl, being careful not to undertighten so that water leaks, and not to overtighten so that the tank cracks and you have to go back and return it and buy another complete toilet (you most likely bought your toilet at Home Depot, Menards, Lowes, or Ace where they don't sell the tank separately in nearly all cases). Your all in cost for this project is at least $88 for a new toilet from any of the places I mentioned, plus possibly extra $10-20 for replacement bolts, water supply line, and extra wax ring. Presuming the hardware store is 5 minutes from your house and you only had to go there once, you used about 2 hours minimum, or maybe several days to complete this. Now you have an old toilet to haul out of your house. Depending on your local codes you can either set it out at the curb, hide it in your backyard, or take it to the landfill. This one is less desirable to move around since it has been used many times and isn't as clean as the new one you just installed.
Your second option is to hire a plumber. A plumber will be scheduled and someone must be home while they are there in most cases. They typically don't schedule to the hour but rather "in the morning" or "in the afternoon" because they have other jobs that have to be scheduled as well and they don't all go as planned (which you certainly learned if you took the first option and replaced the toilet yourself). The plumber shows up and is well prepared. He has extra wax rings, extra hoses, all the tools needed to do the job, and can possibly even grind up tile if needed to accommodate a toilet install where the previous owner tiled around the old toilet. He carries everything in, installs the toilet in 30-60 minutes, cleans up neatly after himself, and takes away your old toilet to dispose of in his dumpster. He didn't buy your toilet at Home Depot (unless you chose the option of having Home Depot do the install themselves), he bought it from a local plumbing supply. You will be charged retail price for the toilet, a service call fee, and an hourly fee. Your total cost for a very basic but functional toilet install by a plumber in 2016 is likely to be around $300-500. You will have not had to lift a finger, get dirty, and you'll feel good knowing that you are using less water per flush than your old toilet, so you helped the environment out, right?
Your third option is to replace the toilet tank lid. The majority of our toilet tank lids as of 2016 are $50 plus the shipping option you choose, but we do have some rare ones that are hard for us to track down that we have to pay a premium for and may cost $75 or more. You can either order the tank lid 24 hours a day on our website, or if you need assistance determining which lid, you can text or email us a photo and we can identify the lid you need, even if it is broken or missing. We normally identify the lid within minutes or at least within 24 hours, even on weekends. You can do this all from home without having to go to a store. We will pack it up professionally and ship it to your doorstep via UPS usually arriving 2-5 business days after you order. It will be waiting for you when you get home from work or wherever you might be. You will open the box, place the tank lid on your toilet, and throw the broken one in the trash. You can keep the box to wrap a birthday or Christmas present or for storing something in your basement/garage. You are a little concerned that you could have replaced the toilet to save on water usage, but then you remember you did an even better service to the environment. You kept your original toilet that was already produced years ago in service and out of a landfill. You purchased (in most cases) a salvaged tank lid that we bought from a plumber or salvage yard, and we are keeping it from going into the landfill. While a new toilet might use less water per flush, studies have been done that show that manufacturing a new toilet uses a LOT of resources such as water and fuel to get it from Mexico or China to your house. Keeping your toilet is much friendlier to the environment in most cases.
So it is up to you to decide. You can buy a toilet tank lid for (in most cases) well under $100. You can do a lot of time consuming manual labor and pay at least about $100. Or you can hire a plumber and pay $300-$500 plus an afternoon or morning of your time waiting around the house. We know that the smart move is to replace just the toilet tank lid in nearly all cases, but you can decide what works best for your situation.