The easiest way I've found to replace mine is:
1. find a long board that will prop open the door. I have a couple of 2x2s that I use.
2. With the door securely open, there is a little collar on the rubber end of the gas prop. Lifting it slightly with a small screwdriver releases the ball on the mount. With one end of, it is very easy to release the other end the same way.
3. Slip the new gas prop on the inside mount, pup the collar and seat it on the ball. Repeat for the outside end.
I've put two new props on a door in under two minutes.
Be sure to measure the stroke carefully before buying. There are several different sizes. The combination of the pressure and the stroke can make it easy to end up with the wrong size.
2000 Georgie Boy Landau 36' DP
2005 Saturn Vue toad