I used ramps for the back end - so I was already up 3" off the garage floor. Dropping the tire down opens up a great deal of room to maneuver.The alternative is raising the GX higher so that you can get the proper angle to remove the small bit of piping in front of the axle. This will help on reinstalling the dump pipe as well.
If you are limited on how much you can raise it, dropping the spare is less of a headache.