Getting a new grip onto a throttle sleeve is no problem: spray a little carb cleaner on it and slide it on. Getting a new grip OFF, after you realize that the tube is problematic is kinda difficult. Especially if you want to save the grip itself.
Here's an easy way to transfer the grip and aggravate your wife in one go.
Step 1: Put the Kettle On.
Literally. Bring your grip assembly and the new throttle tube home with you, taking care that the fresh grease you've slathered on gets all over the inside of your bag.
This is really only a 2-step process. Boil some water, put the stuck grip in a tall cup ( I used one of my wife's souvenir cups from Mardi Gras, this fulfilling the second part of this I'ble).
Put a little drop of soap on the grip an pour the boiling water over it, filling the cup.
Step 2: Grab Some Paper Towels
1. Using your wife's William Sonoma towels is apparently going too far.
2. It's going to be hot. (duh.)
Let the grip soak for 30-45 seconds. At that point, pull out the assembly and use the towels to twist off the grip.
Then, while the grip is still warm, slide it on the new throttle tube.
Now sit on the couch and vroom vroom while holding your new grip assembly.