Don't take offence but your question about engine upgrades fits into the "how long is a piece of string" category. That said, your options are:
- upgrade the Type 1 engine you have. This is likely to be the easiest route as you are replacing like with like and parts are relatively cheap. (Type 1 = Beetle engine)
- Swap to a Type 4 engine. I think I read that this was big trouble but can't find the link...
- Swap to a water-cooled motor. Most significant power increase but also most $ and effort.
As for the type of camper, I would guess a Dormobile. Check here for more info:
http://www.aussiekombicampers.com/conversions.shtml