You have done well to find one with all the original brasswork still intact. At that age so many are missing an escutcheon, or have been dropped on the handle or whatever.
As said, removing the action is a simple job. If it has never been removed it might take a bit of time to locate all the screws, but be patient and you should be fine. They had an annoying habit of grinding off part of the head to make it flush and then filling the slot with some filler. That comes out easily enough but be careful because the grinding can leave the edges of the screws quite sharp- so watch your fingers. I generally tap out to a modern metric size and use new allen bolts, but on a unit as well preserved as that I would leave it all genuine.
Your locksmith will have appropriate blanks. I don’t remember them being anything unusual for that model. You shouldn’t have to mention to a good locksmith- but do so any way. Ask him to alter the sequence of the levers so that if anybody still has the original key it will no longer function.
Paint types, I am afraid I can’t help you!
