The model that uses the stock throttle sleeve is not going to fit right, I believe. Do some searches here, the search function works well, but as I recall someone bought the black one that goes over the sleeve and it is so tight the sleeve deformed causing the throttle to bind.
http://www.kuryakyn.com/products/3798/iso-grips recommends the 6236 for the R3's.
I haven't actually installed one, but with a built-in sleeve it should be a matter of opening up literally two bolts, disconnecting the stock grip, putting the Iso-grip in there, hooking up the cables and tightening the bolts.
Of course, you may have to peel the bear claw and assorted other bits and bobs off the side of the bike and loosen the throttle cables to do that... not hard, just takes a little time and it's a bit cramped to get in there.
But since the one that reuses the stock sleeve is probably too tight, your choices aren't many.