I pulled the stacking set out and took the dryer off of the top (with help). I tilted the appliance up to remove the old feet and installed the new ones set to the lowest height (one side at a time). I slid the washer in by itself to test level (it wasn't). Got all four feet in firm contact with the floor. The front was slightly high, so I slid the washer back out, raised the back a turn, and slid it back. I fine-tuned the level from there. Slid the washer back out for the last time, reinstalled the dryer on top, reattached the hoses and tubes, and slid the whole thing back in place.
This would've been a lot easier with self-leveling rear legs.