Replacing the power window regulators is not too bad a job. The door
doesn't need to come off. Only the door panel. You've already done
that once, so you're halfway there. The procedure is documented in
the Bentley manual. There are a lot of little things to deal with
(bolts here, tie wraps there) so it best to read the stuff over in
the Bentley.

I'd suggest getting the existing one out and examining it. It might
be possible to repair. There is no "tensioning" involved as the unit
is complete unto itself.

When mine broke, I ordered replacement, installed it, and then fixed
the "broken" one as a spare for the next time. Then again, I've got 4
vanagons, so the next time for me is likely to be a lot sooner than 1
vanagon owners....