David,

Can't help as far as getting the O2 sensor out, but...

Just a few weeks ago, I replaced that section of pipe on my 85.  Yes, the Bosch
sensors are expensive ($60-80); however, your FLAPS can get you a "universal"
one that requires a small bit of wiring on your part, for about $20--apparently
works just the same.

As for the gaskets--yep, just carefully scrape them off if necessary (and
remember to lightly sand the surface before reinstalling.  My problem wasn't
with getting gaskets off, but with getting the darn old bolts out.  Had to heat
them up with a propane torch and punch them out--a real pain.

Good luck,

David Bradshaw
85 vanagon