Only too happy to supply diagrams if required... On the battery discharging overnight, this may be due to an old or underrated battery. Also when you've got a few moments check for excessive drain from the battery with every thing switched off. There is a great deal of information on the site regarding parasitic drain (quite often caused by a faulty audio amplifier) - If it is this just pull the fuse and check again. On the subject of the fifth door, there are reports of this on the site but have never heard how (or if) it was resolved. Pity you live so far away as I have a donor GV (2006) with a power rear door that works fine (died of gearbox failure), as bignev said this sounds like a precursor to the TCM providing another challenge. When I bought the donor I spent a bit of time trying to fix the gear problem - resolved the all gears lit up problem (wiring problem) - thought hey ho but did not resolve the gearbox problem - kept changing gear at will .. but that's another story.
Good luck with your project (don't want to be pessemistic but it's enough of a challenge keeping a normal GV on the road.. (Yes Bignev, I agree, there ain't no such thing as NORMAL with respect to the GV..