just bought my dream car, have a few questions

1) When I got my '82 turbo about 6-8 years ago, I was in the same boat. The turbo didn't work. I drove the car around a bit, but it ran so bad, I stopped until I had the $$ for another turbo unit. I found a good one at a Nissan-only wrecking yard for $200 that worked flawlessly until I sold the car 2 years ago.
So my advice is not to drive the car with the turbo not working. I don't know if it hurts the engine, but it sure doesn't help it. I would also not even DREAM of switching manifolds. That is a huge job (you'd have to do the exhaust pipe too, I think) and guess what, the car would still run like crap because it's a low compression engine that needs the turbo to run right. Everything in the whole fuel management system (which is completely different from an N/A car) is totally different and geared to work only with a turbo. So do yourself a favor and put a new one in there.
2) This is one of the best websites for all Z stuff, including turbos.
3) No personal experience here, but I don't know how you'd hook two turbos up to an inline 6. The twin-turbo 300ZXs have a turbo for each bank of the V-6, which makes sense. The way to go with an inline is simply one bigger turbo, which is done all the time. Check the archives.

.....1. it wont hardly run @ all w/o the turbo.......
......depends on what wrong w/the turbo you got.....i dont feel i could (most people could) do it as well as a good reman place.....
2......this is as good as any.....www.hybridz.org is good too
3...yeah..its a real big deal that requires a lot of knowledge,resources.. (prbly $$$$ too)....ultimately 1 big turbo will prbly get you more w/a straight 6....from what i have heard...."i think" the twin turbos are v6's (not sure).....but if they are you have 3 pipes on each side (instead of all 6 on 1 side)...so they use 2 turbos....they dont have much more hp than some of the single turbos.....
....theres alot to do before you "out grow" the original turbo..you can prbly get 3-400hp out of the stock turbo...i imagine @ less than 400 your engine internals would give out.......and its hard (or maybe you cant) get enough fuel to go w/the air w/o changing out electronics and a bunch of other stuff.....
......i'm in the middle of intercooling my 82zxt and replacing my injectors w/370cc merkurs.....once i modify my wastegate and pop-off valve (or get a boost controller)...and open up my exhaust i hope to have 3-350hp......then a quaife lsd (or something) to get that to the ground ....... outta be enough to kill myself ....or @ least get some speeding tickets......s