I posted on this a few months back "or so" but need some more advice / info.

Background info: Car is a 1989 745ti, 140k mi. Replaced the turbo a few months back with a ported TD05h 14b from Cherry Turbos. In replacing the turbo, Herman recommended that I replace the oil feed line. In order to do that, I had to remove the oil filter extender assembly (the big-arse banjo bolt that comes out the side of the block where the oil filter is located on non-oil cooler equipped models...?) In doing so, I didn't heed anyones advice and forgot to replace the gasket located within. Well I paid dearly for it. About 1 qt every 500 miles dearly. So now I'm faced with a predicament: to take the car to the dealer or not?
Dealer quoted me 3 hours of labor to do this job. That's $220. Tack onto that, the fact that the car has been the testbed for my performance modification ideas... i.e. no cat, no rear muffler, lots of JB Weld where things "didn't quite fit", an electric fan, 3 row HD radiator, boost controller, cam, gear, cold air intake cone filter w/heatshield 'etc.'
In my experience, Volvo factory certified mechs and techs frown on working on modded cars, and from time to time have reported those of us who decide to drive without a cat and create our own personal hole in the ozone layer. SO onto my actual questions:

Any recommendations on how to do this job with the turbo / exhaust manifold in place? (B230FT) I did it while the turbo was out... now there's a whole lot less space in there to work with.

What size is the head on the banjo bolt? I've heard 25 mm, but I had a spare 34 mm socket laying around from a prior job, and it was just a little loose but it fit. So I'm thinking more around 30 mm, sound right? I couldn't find the specs anywhere!!

Sorry for the long wind, and thanks for any advice

Ryan