I thought I'd try my hand at disassembly/repair (my first time with any camera).
General advice, learned the hard way:
As mentioned, for tight screws you should grind/file/sand the screwdriver to an exact fit.
Work on a plush white towel: It will catch little fiddly bits so they don't roll to the ground; keeps the camera from getting scratched; prevents slipping.
When faced with a recalcitrant screw, don't be afraid of picking up a _small_ drop of WD-40 on the tip of a toothpick and applying. Knock the screw to set up small shock waves to help get the WD-40 in between the threads. Leave in a warm place for several days, knocking the screw head now and then.
As you take it apart, take lots of pictures with a digicam, take lots of notes, and have a mini voice recorder handy for spoken notes. Especially note the position of the hairsprings and longest screws.
When undoing helicals make marks as to how things line up when assembled. Also mark the points where the helical comes apart so you can get it started on the right thread.
Make scratch marks across meshed gears so you can put them back 'in-synch'.
Keep screws and parts for each sub-assembly together on the the towel - the towel will keep the parts separated.
Don't take anything apart any more than you have to.
Mechanical linkages, shutter mechanisms, self-timers & stuff are best cleaned with lighter fluid.
Don't use 3-in-1, sewing machine oil, household oil, penetrating oil, WD-40 etc. for lubrication. Plain old SAE 10W30 engine oil works very well and won't gum up. If you need something lighter then try ATF. The best, of course, is a proper clock oil from Nye.
Helical grease can be hard to come by: you need something that doesn't separate. The best is Corning vacuum fitting grease. Grease for disc brakes, available at the auto parts store, also works -- see if they have it w/o any moly. The grease sold for lubricating helicals isn't very good because it dries out - as you already know.
