The rear wiper motor had seized up due to dirt and corrosion (gravel roads), so I needed to take the rear gate trim panel off and decided to kill two birds with this stone. The rear panel comes off starting with the top panel above the glass. The side panels are next and will come off pretty easily by lightly prying at the base of the round plastic clips. The tricky bit is the main portion of the panel - it comes off after loosening the side clips and then popping the clips at the top and pulling/moving the trim panel down.
For parts, if your rear wiper motor just clicks and gets warm to the touch, you'll need a reman wiper motor assy from AutoZone or some place similar. I looked at Rock, but there was no $$ advantage that I saw to going with one where I couldn't just hand in the core. It's pretty simple, so I won't get into that here except to say that it rests at 3 o'clock.
For the rusty license plate nuts, you'll need a pair of vice grips and one of those multi-size drill bits (if you want to make it pretty). I chose the ugly route since this van is no prom queen. By rocking back and forth with the vice grips, you'll be able to break them loose and you'll be left with a hole like this one. If you wiggle the nuts too far back and forth, you may have to hammer/dolly the panel back flat, but you'd really have to work to mess it up too much.