I would say they are pretty collectable, maybe not up there with some of the Tamiyas of that era but definitely interesting. I think it was quite advanced at the time.
Very stylish buggy, maybe one of the best ever?
Yours looks in OK condition - parts will always be hard to find, ebay is probbaly your best bet, or go to www.tamiyaclub.com
, that seems to be the website that most of the RC collectors out there congregate on.