There may be some "work and play" type trailers that would fit a jetta, but I doubt you'd be able to find one within your limits. That, and the work and play type trailers are very very sparse for actually camping in them.
The Nissan Titan has a similar rear window, but it's about 75% of the window that rolls down, not the entire thing. I test drove one, but it's a dated truck and probably not a big upgrade over your tundra. I'd take a tundra over a titan any day.
I second notion that RVing will not save money. It's a purely luxury item, and with it comes added expenses. All of us here LOVE RVing which is why we do it.... none of us do it to save money. On a trip vs trip basis, yes you'll save on hotel costs if you're normally staying in nicer hotels... but the high $ entry fee into the world of RV's, coupled with the extra fuel spent, regular maintinence, and all the extra stuff you will inevitably buy, will put you way over the cost of a few hotel rooms.
That said, it truly is a wonderful way to vacation. I really feel my family is as close knit as we are, due to our camping trips growing up. It's hard to describe the joy it brings us "campers", it's hard to say why exactly we love it. If you DO buy an RV, you're entering a world of wonderful helpful people, endless vacation possibilities, and a lifetime of memories for you and your family.