Well, I'm no pinball expert by any means but since your auction is so close by and in just a few days I'd definitely wait. There is no guarantee on the quality of anything sold at these auctions, however, and once you win a machine it's yours.
From the few superauctions I've been to you have to be very careful what you're buying (as far as pinballs go). The ones I've seen looked very good but after playing for abit you realize some bumpers don't activate, relays don't respond, some get stuck, etc. Just be careful and test!