Setting and hooking up a toilet is a surprisingly simple operation. With an existing fixture, shut off and disconnect the supply line, flush the tank, then swab out remaining water with an old towel or sponge.

Older tanks attach to the wall via screws through the
rear and have an elbow connection to the bowl.
Disconnect these and remove the tank. If the tank
sits on the bowl, the toilet can be removed in one
piece, but separating the tank and bowl makes them
easier to handle. Pry off the caps covering the bowl's
hold-down bolts. Remove the nuts-or cut with a
hacksaw if they're rusted on. Lift the bowl off the
flange. Keep the flange in place. If it is damaged,
you may have a large job that calls for a pro.

Before you install the new bowl, temporarily set it on
the flange and check for level. Shim, if necessary,
with rustproof metal washers. Lift off the bowl again,
turn it upside down, and fit a wax ring seal around the
bowl's outlet. Run a bead of plumber's putty around
the outer rim of the bowl's base, so dirt and water
won't get underneath. Set the bowl in place, check
for level again, and install nuts on the hold-down bolts. Tighten until snug; don't overtighten or you may crack the china.

Fit a spud washer and the tank over the bowl's inlet opening, secure with bolts, and hook up the water supply. If there is no shutoff valve on the supply line, this would be a good time to install one. Set the bowl in place with a slight twisting motion but don't rock or lift it again-you could break the water tight seal. Finally, cut on the water supply and check for leaks.