[Normsthename]

If you want to use the grips again, and remove them without damaging them. Best method I have found is to use a WD40 aerosol or similar with the tiny pipe that comes with them, push the pipe down between the grip & bar and spray. This will loosen it a little, continue doing this until you can remove the grip.
Replacing the grip, you will need to fully degrease the bar & grip. I find brake cleaner to be the best because it evaporates so quickly.

Hope this is of some use

Andy