you can try electrical section of this board, or try ask PapaJam, he has some excellent wiring diagrams for our alfas, as about service manual, you can try shop manual from IAP, there are also some on CD, like cardisk.
I have the copies of shop manuals & owners manual on CD from Car Disc. (<- link) It also includes TSB's, the convertible top manual (which shows how to adjust the windows), and copies of Alfa advertisments.
For general information about Alfa's & advice about things the home mechanic can do, get some of Pat Braden's books about Alfas.
The best wire diagrams are the ones that fellow BB member PapaJam offers. He'll email you copies and suggest a donation to the BB. Please consider doing so as this BB will be one of your best sources for advice about your Alfa Romeo Spider Veloce.