If ceramic, you have to remove it and start over, if vinyl, just go on top of the existing tile, you will have to buy new shoe molding or 1/4 round since your floor will rise 1/32 of an inch. Caulk good around all fixtures.
Most important thing to do is to make sure that the floor is void of all debris. The smallest particle will look like a big hump and wear faster under your new.
Get good vinyl that has allot of good stick stuff on the back. Cheap tile is not sticky. Test the stuff first. Good Luck,