Ok Im a bit tired but lets see if I can add some more to this. FIrst if its an 01 rc51 chances are its not a usb power commander. In such a case you will need a serial cable to hook up the pc to it. Not a big deal jsut buy the cable at compusa for lole 10 dollars.
You definately want one on your rc. As good of a bike as it is the power commander with a proper map for the pipes makes it a completely different animal. Stuff to look for is the free mods which most maps take into consideration. These include the flapper mod, softrev(can make the kit for under 2 dollars) and some times the pair valve removal which really doesnt add power but tkaes away some weight and clutter.
A great place for info is
www.rc51.org. Can surf a lot of the site for free. Look up the mods link. If you do end up getting the rc then pony up the 20 dollars for the lifetime membership. A lot of good guys there and they really know their stuff about the rc51.