I would pull the stock off. Lightly sand with 400 grit. The problem is the bare wood may be oil soaked, wipe down with acetone and let dry for a day. Put a small dab of finish (tung oil) on and let sit for 5 minutes then wipe off. keep applying finish and wipe off and let dry between coats. Only use the acetone on the bare wood. Don't use it anymore once you start putting oil on. The bad spot on the front of the lock may have gun oil in it. The best way to get that out is to use arm and hammer oven cleaner. Put a small amount on the darkened area and let sit for a few minutes and see if the foam turns a nasty brown. If it does that means it is pulling the oil out. If not, it may be a burned spot. You may have to lightly sand down with 400 grit paper. to the bare wood. Be sure on the oven cleaner to wipe off and let dry for a day or 2 before putting finish on.