A few years ago I replaced my old water wasting toilets with new water efficient models. Not wanting to pay what the plumber was asking for installation, I learned what it takes to install a toilet. The process is actually easier than it sounds. If you are in the market for a new toilet, a self install is a very viable option.
The team at Home Depot has made a great video about the subject. The presenter does not get dirty, which probably is an unrealistic assumption.
Remove the old toilet
Removal of the old toilet begins with emptying the tank. Turn the water supply off and flush the toilet. This should nearly empty the bowl. Remove any water that is left with a sponge. Disconnect the water supply hose at the base of tank.
The toilet is held in place by two bolts. Remove the bolt covers and remove the nuts. The toilet can now be lifted off the toilet flange.
The toilet's tank does not have to be removed, if you are comfortable lifting the toilet base and the tank as a unit. Lift the unit by holding on to the base. The bolts that connect the tank to the base were not designed to allow the whole toilet to be lifted by the tank.
Lift the toilet off the flange and set it aside. Any resistance you feel is the wax ring's seal slowly letting go. The wax ring, a ring of wax that seals the joint between the toilet and the toilet flange, will either stick to the toilet or the flange. Clean off any remnants from either surface.
Next clean the area. Pay special attention to the toilet flange. Any lose debris in the area could cause the new wax ring to fail. Debris on the floor might not allow the toilet to sit level.
At this point the area is ready for installation of a new toilet. Either reinstall the old toilet, or a new one. The work required is the same.
Before installing the toilet inspect the toilet bolts. Being close to the wax ring, they can get pretty dirty. It can get pretty difficult to get the nut all the way onto a dirty bolt. Since bolts are cheap and readily available, it's often easier to install new bolts than to clean the old ones. Wax ring and bolt sets are available at all home centers or online.
Next determine how many wax rings you'll need. If the toilet flange is installed to spec, one will be enough. If the flange sits lower, a second ring might be necessary. A third ring is not an option. In that case the flange needs to be redone. The combined height of all wax rings should be just a little higher than the distance from the flange to the base of the toilet. When the toilet is set onto the ring(s), it will compress the ring(s) and create a water tight seal. Without compression there is no seal.
Place the wax ring(s) onto the flange and lift the toilet into place. I find that this technique is faster and easier on the toilet than turning it upside down and applying the ring to its base. Either way will get you there.
Tighten the bolts until the toilet stops rocking. Don't over tighten or you'll risk breaking the bowl. If the toilet does not move when it is being used, the bolts are tight enough. The wax ring creates a water tight seal long before the toilet stop moving. Tighter is not better.
Caulking the seam between the toilet and the floor is not necessary. The wax ring will keep any water from escaping the toilet. The caulk actually only prevents water from flowing in. If you regularly soak the floor in the toilet area with water (coming out of the shower, cleaning, ...), caulking the joint might be a good idea. Otherwise you can skip this step.
Reconnect the water supply and turn the water back on. Test for leaks with a few test flushes.
Replacing a toilet is within the reach of every homeowner. It can be done in minutes and there is very little than can go wrong. This is not a project that requires the expertise of a plumber. Hire a handyman if you want to have it done for you.
If you are in the market for that new toilet, bring it home and install it. Installing a new toilet is one of the simpler things you can do yourself.