Thanks everyone for your input.
Based on the suggestions here, I took a closer look at the inside of the rear door frame. With barely enough room to work, l removed two screws that held a thin panel in place. That uncovered another two screws that hold the light assembly in place. Swapped out the bad bulb, put it back together. Done.
Wishing everyone many happy and trouble free miles!
The left rear lens cover is not screwed in place. It appears to snap in place. I don't wish to break anything trying to remove it. Can those of you familiar with this Model Roadtrek offer guidance on how to remove lens cover? Thanks