1. Pick up some WD40 and a can of compressed air at Office Depot.2. Remove the throttle housing.
3. Remove the bar end.
4. Remove the throttle cables from the stock tube.
4. Pull the grip and tube off the handlebar.
4a. Careful, the grip is hardwired to the bike due to the heating elements. You might need to feed some extra cable through the bars to give you enough cable slack to remove the grip/tube.
4b. Remember the position if the grip, i.e., the position where the heating cable meets the grip. You'll need to ensure the grip goes back into that same position, so that the heating cable doesn't bind or stretch as you twist the throttle.
5. Use the WD-40 and/or compressed air to jet into the space between the tube and grip to loosen and remove the tube.
6. Spritz some WD-40 on the G2 tube, if necessary, and work the grip back on it.
7. Put the new tube/grip back on the handlebar.
8. Adjust the rotation of the grip, so that the heating cable is located properly, re item 4B above.
9. Hook up the throttle cables. Their locations are obvious.
10. Re-assemble the throttle housing.
10a. The throttle cables have little plastic dealies that insert into little slots on each half of the assembly. The heating cable has it's own little hole, with a rubber gasket on the cable to weather-proof it. You gotta align all these bits for the housing to snap back together.
11. Re-attach the bar end.