Barring any problems, it's straight forward -- but call in one of your male friends to do the lifting. You'll typicall take out the old toilet in one piece and it's heavy/awkward.

I think there's an article here detailing the steps but basically this is it-

-before starting, have on hand-
---new toilet
---TWO wax rings (just in case you have a problem the first time)
---mounting bolts (comes in a kit with all the bolts/nuts/washers you'll need)
---supply line hose
---supply valve (assuming you need to replace it, which I almost always do

Then-
-clean the toilet (you'll getting up close and personal with the toilet as you remove it, so you'll want it squeeky clean)
-assuming the toilet was caulked, use a utility knife to cut the caulk seal between the bowl and the floor.
-turn off the supply valve
-flush and hold the lever to drain the tank
-fill the kitchen sink or a large pot with hot water, and put the new wax ring in the water. Leave it till we're ready to install the new toilet
-sponge out as much water as you can from the tank
-plunge/bail out the water from the bowl. A wet/dry vac works really well here. If you don't have one, a small paper cup works well to bail.
-remove the nuts holding the toilet to the floor
-at this point, if you've got a grunt laborer, you're ready to lift up and remove the entire toilet. Put down a drop cloth or large plastic trash bag so you've got some place to set the toilet down once you've pulled it off. If you're on your own, the tank is removed by undoing the two bolts holding the tank to the bowl, and this makes it much more managable. However, if this is an old toilet, the screws will most likely be corroded. If you can't get help, and can't get the bolts undone, as a last resort, you can use a hammer to smash the tank. It will break into shards so wrap the whole thing in a sheet first.
-once the toilet is up and out, use a putty knife to remove all of the old wax seal from the mounting flange in the floor. This stuff is thick and sticky, so have a bunch of rags handy and a trash bag to throw it in. The old mounting bolts are probably corroded, so remove and replace them while you're at it.
-if your supply line was one of those corrugated flexy metal tubes going from the valve to the toilet, it will probably crack and leak when you install the new toilet. I ALWAYS replace these with a flex hose while replacing the toilet. Do it now while the toilet's out of the way. If you do have one of those flexy pipes, you'll probably find that it was built into the valve and that it's necessary to replace the entire valve - which means turning off the water supply to the house. Check this out BEFORE you start the job, and have a valve with the appropriate connector type/size on hand before you start. Typically, you'll either have a threaded pipe coming out of the wall, which requires a valve with a FIP (female pipe) connector, or you'll have a copper pipe, and the valve will require a COMPRESSION connector (typically 5/8" -the outside diameter of a 1/2" copper pipe).
-turn the new toilet bowl upside down and install your now nicely softened wax ring.
-pick up the bowl, flip it over, and set it down on the mounting flange, pressing straight down. It helps to have a second person to help guide it down onto the bolts. Being careful to press straight down and NOT ROCK the bowl, put your full body weight on the bowl to get a good seal.
-install the nuts on the flange mount bolts and snug them down.
-install the tank. This varies from toilet to toilet, so follow the mfg's instructions. But basically it's just a matter of inserting a rubber gasket between the tank and bowl, setting the tank on top, and installing the two tank-to-bowl bolts.
-reattach the water supply line, turn it on and check for leaks
-once you've verified that everything is right and leak free, run a bead of caulk (silicone, mildew-proof) around the base of the bowl and the floor.

That's it! Just put the old toilet out for the trash and you're done.