That is a great looking machine you have gotten! Mine has progressed very well but is on hold at the moment. While cleaning everything before reassembly, I discovered some pitting in the boiler that was almost all the way through. I brazed the pitting and reinforced the bottom with new copper, then cleaned everything again so the boiler is stronger than new. At about the same time I got an offer for everything in as-is, un-assembled condition. I'm waiting on this to work out and... if it doesn't I may actually be fabricating 3 smaller boilers and making 3 single group machines with electronic pressure transducer controls and PID... new san marco lever steam and water valves and custom tig welded one-off frames and body pannels rolled on a french wheel. If the deal does go through, it would save me some work but that's all to be seen. I have a few machines in the works right now (frame up rebuilds) for 2 buddies so that has delayed me too. If you want parts, you can get everything from nuova ricambi US at http://www.nuovaricambi.us/Catalog.cfm
or you can get them from espressoparts here
http://www.espressoparts.com/GaggiaItaliaLeverGroup
The valves and sight glass are an easy rebuild and the group is not too bad to work on. I just did a repair on a similar machine for blue bottle here in nyc check this video:
http://www.youtube.com/watch?v=epzQFXI7ES0
It came out well and...even buffed the panels to a high gloss. the video only shows the machine sans-panels but you get the idea of what great shots it pulls. best wishes on your rebuild - be sure to check for pitting on your piston walls.

Almsot forgot... if the offer I have for everything doesn't pan out I'll get back to you guys whot may be in need of some of these extra parts ASAP. I have lots I won't be using.