It's not that hard of a job and there should be instructions that come with the grips. By the way, iso grips are a lot more girthy than the stock grips and shoul feel way better in your hands. I'm pretty sure they are also longer too. Makes a definite improvement to the appearance in my opinion as well.
Their are some tricks to removing those old grips without many issues. Member Nomad posted this brilliant idea for removing grips:
Easiest way with no damage to the grips should you ever want to use them again. Remove the bar end weights, work a thin bladed flat screwdriver between the inner edge of the grip and the bar, spray WD 40 through the plastic straw that comes attached to the can into the gap alongside the screwdriver blade. Work the blade around the inner side of the grip and the WD 40 will disolve the grip glue and enable you to slide it off the bar in one undamaged piece.
I ended up cutting mine one of mine off with a razor blade b/c I didn't know of this trick before changing mine.
