I have not, but you have the option of
- Running the good tire up on a ramp to leave the one to be changed hanging in the air about 3 inches of ramp required), or
- Lifting the trailer by jacking.
If jacking, the frame behind - but as close as possible to - the trailing (rearward) wheel is the preferred location. There have been previous discussions of jacking points and techniques in this forum.
Yes, loosen the nuts before all of the load is off of the wheel (so it doesn't turn), unless you are using an impact wrench; however, just barely loosen, don't remove them or even back them off significantly.
Of course, you should chock the opposite side tires.