The wife and I bought a steamer for $50 from Lowe's. The good news is that it can double as an engine cleaner.
It did make the drywall damp, but we used plastic putty knives and didn't score it too bad. We did have to patch and sand some spots. Overall, the wall looks much better...
The upstairs of our house has 5-6 coats of paint
over the wallpaper....