I've had quite a few American hammer guns that I'm sure never had the locks off in over a 100 years. On any of those that I've taken the locks off of, the left hammer has to be removed many times to get to the screw running from the left lock to the right lock. If it's backed off a couple of turns, the back side of a screwdriver can be used to tap on the screw head. This will unseat the right lock. Continue to remove the cross screw. It can then be used if left in its hole just a bit to pry the back of the left lock out a bit so it can be removed. The right lock should be out a bit, but again the same screw can be used in it's hole to pry a bit. The front of the lock plates have a small extension that goes in the receiver. That cross screw is what hold the back half tight against the wood. When putting the locks back in many times the triggers have have to be kept forward so the sears will fit by them.
You get the locks out and some WD-40 then some compressed air to blow them out followed up by a little oil is all it should take. I wouldn't go any farther than that unless you have some working knowledge of how the locks work. You'd need a spring vise to compress the main spring. And it's very, very easy to break off the small pin sticking out of the spring into the lock plate. Good luck finding another. It's not that hard to take them out, clean and oil em back up. Good luck.
