Tools needed will be as follows:

1. A flat screwdriver

2. An adjustable wrench

3. A utility knife

4. A pair of adjustable pliers (Channelocks)

5. Hacksaw

6. Rubber gloves

7. A piece of cardboard big enough for the commode to sit on.

8. A few old towels that can be discarded afterward.

9. A new commode complete with new seal and hardware.

First thing to do is to clean the inside of the bowl. Use bleach (or another cleaning agent which kills germs) and brush then flush it a few times. This is to kill all germs because your hands will be going inside the bowl later.

After thoroughly cleansing the bowl turn the water off going to the commode. Flush and hold the handle down untill all the water has run out. (note: There will still be a little water left in the tank). Take an old styrofoam or plastic cup and dip out as much water as possible from the tank. Use an old towel to soak the rest of the water up.

Now you're ready to empty the rest of the water from the bowl. (I know you're going to love putting your hands inside it aren't you). Take the cup and dip the water out as much as possible. Use the towel to sop the rest of the water out.

Place the towel under the cut off vale and remove line from commode tank. There will be a little water come out but the towel can handle it. Remove the bolt caps at bottom of bowl, one on each side, to expose the bolts. Using the adjustable wrench, remove the nuts holding commode to floor. Place the cardboard in the bottom of the tub to set commode on when removing it from its place. (note: This is just in case there may still be water on the bowl trap).

Where the commode was sitting you will see what is left of the wax seal. This must be removed completely. There is most likely a cone which likewise must be removed. Get the flange as clean as possible. Use the screwdriver if you must to remove the old wax. I prefer to use something I can throw away later.

Take an old towel and stuff it slightly inside the pipe to stop the odor from coming through. (note: Towel will be thrown away shortly). Be careful not to push it deep inside the pipes because it must be removed before installing the new toilet.

Remove towel from inside pipe and throw in garbage. Place new bolts in slots where old bolt were removed. Place new wax seal in the commode flange. Set commode bowl carefully watching to make sure both bolts come through bolt holes. Push commode gently down applying pressure as evenly as possible. Try not to rock it. Put washers on bolts according to the directions that came with your new commode.

Put nuts on bolts and tighten. Be careful to not tighten them too much. Over-tightening can break the bolts, the flange or even the commode. You want the commode to sit solid on the floor. This can be achieved without over-tightening the nuts.

After the bowl is set, place the tank to the back of it according to the directions. There are many different ways to connect tanks to bowls. There are many manufacturers and most are done different than others. It's basically the same. Do not over-tighten the fasteners. Commodes and tanks are porcelain which is strong but easily shattered.

Connect flush handle to flapper inside tank. Some may be connected from the manufacturer. Those that I am familiar with have chains that must be connected.

Connect your water line to the tank. Most of them need only be hand tightened. Some require tightening with pliers or a wrench. Turn water on and watch for leaks. Keep a check on the water level in the tank. There will be a line on the tank or the overflow tube showing the proper water level. Adjust according to manufacturer to get the desired level.

After finding no leaks and you are satisfied with your project use the hacksaw to cut off the bolts flush with the nuts. Place bolt caps over bolts and snap them into place. Replace commode seat using flat screwdriver.

Dispose of everything according the the laws and regulations of your state or community. Littering/dumping is a no-no in every state and is punishable by fines and/or imprisonment if caught.

I hope this gives you plenty of information and helps you to install a commode. If something comes up, you can mention it in comments and I will do my best to answer. I have worked a lot of my life in construction and have seen a lot of things, but I don't believe I've seen it all yet.