You mentioned gun smith screw drivers, I would make sure that for each screw head the screw driver fits perfectly in the slot as to width and length.
Removing the lock, use the screw from the left side and screw it into the right side and lift it off. If it is too snug try gently tapping the head of the screw. If still too hard from oil solidifying under the lock/s, well just hope that does not happen because removing the stuck lock could tear out some of the thin wood. It might have to be lightly heated with a soldering iron.
The screw under the top tang pulls the trigger plate assembly up into the receiver, it is always good to measure with a dial Vernier caliper to get the right dimension in going back. This screw has a tapered head to the angle of the top tang, remember this when going back. It will take one full turn to orientate the right way, that is why a measurement helps.
If a two screw trigger guard remember which screw goes where as to later for orientation.
