Dirt bike handlebars

Hey everyone, i have a 2003 XR100 four stroke Honda dirt bike and I am on a quest to transform it into a beast hair scrambler trail bike. So far I have decided to add bark busters, one of those bendable hinge shifters, a back sprocket with one less tooth (will be 49), a new front sprocket because the teeth are bent, I need to sharpen the foot pegs and brake peg, a new back tire because the one it has now is bald, and shorten the handlebars. The reason i posted this forum is because i am wondering if anyone can tell me what the best way to shorten the handlebars is. I figure i am going to loosen everything, take it off, measure 4 or 5 inches with a permanent marker, then grind it off, but i dont know how to get the grips off. will i need to buy new ones? any way, if anybody can tell me how to shorten the handlebars, i would be very thankful. also, if anyone thinks i need anything else, could you please mention that too? thanks!