I'm confused, wasn't the vinyl painted? How did you get rid of the black? I'm totally interested in getting rid of the doghouse.
Yes, the ceiling section was painted black along with a small square section on the wall. I tried many different solutions and solvents, and the one that worked best for me was 202 Fiberglass Solvent Wash. That with a brush and many rags got most of the paint off. It was a PITA, though and smelly. It's still not perfect, but it's pretty good.