The first thing to check is the distance from the finished wall (not the baseboard) to the mounting bolts on the toilet. That is your rough-in dimmension. If you are lucky, it is 12". If it is much different than that, you may need to pick up a non-standard toilet. Nearly all of the ones you find in the store are designed for 12".
If your plumbing is vented properly and the current toilet flushes without clogging up, then a well-designed, new, low-flow toilet should be an easy switch-over.
Note, some of the toilets from Toto (the skirted ones) require the water supply line to be wider than the standard by a couple of inches. If you like that look and you are remodeling, then that may be a minor point.