I'l be picking up the donor on thursday, and the life it will have on the drive way will be limited by my girlfriends patience. What are the parts that i need to remove from the sierra? I mean i know it will be the engine and running gear but is there some thing which may be important that i need to get off the car which could easily be overlooked. Or should i just strip the bugger and keep it stored just in case?

Keep everything but the chassis and glass. There's the obvious like the running gear, fuel tank, brakes, pedals, steering and suspension. You can throw away what you don't need form that later once you've decided what you're doing. Other stuff like the wiring loom and seats as well as all switches and lights, (keeping the lights helps understand where all the wires go after you pull it out of the box after 3 months, and you can always sell them off in the free paper later) You are best to keep the carpets if they are in good condition too as they can be used for trim. Mirrors could be useful too.