Should I get this?

Even a 400 is still a B. Plan on a complete strip out of everything cloth in there, especially the carpet, yuck! If your handy with a sewing machine (not that uncommon around here) you could fab up some new drapes, cushion covers and mattress slip covers and have a fresh start. Every carpet i've ever seen in a motor home is disgusting. Many around here have been lived in so wear is heavy. Most old relics need nothing more than a fuel pump and maybe a carb kit. I was offered a class B that needed a fuel pump to make it run. Jusy no room for it it was a 72 and looked old so i can imagine what the inside looked like.