Klaw: The Barrel is rifled using a single cutter rifling machine, such as is demonstrated at Dixon's GunMaker's Fair every July.
( See his Website.
http://dixonmuzzleloading.com/index.php?section=gunmakersfair )
If I were you, I would not hesitate a Day making that trip to Dixon's shop. Chuck is skilled enough to get the trigger/sear/tumbler working again, or repair any of them that is broken.
As to the letters on the top flat, do a pencil rub on paper over the lettering to see it much better. DO NOT polish the top flat OFF to remove crud that is obscuring the letters! If a rag, and some alcohol does not remove the crud, then use a stick of wood to burnish the crud off, but put oil on the surface that is to be rubbed with the stick, so that the crud( mostly oxides) will not become an abrasive and scratch the barrel. Clean the stick's end Frequently! Re-oil the surface any time it becomes bare, or "dry", until you finish the work.
I have used a paint stirring stick they give you at paint stores to do this kind of burnishing successfully, on old metal parts.
The idea is to find ways to remove the crud, and oxides, without abrasives, and without turning the oxides into abrasives that will scratch the metal you are trying to clean. I use motor oil, simply because I have it in my garage for my car/truck. Its heavy enough to coat the metal fully, and helps float the oxides and crud away from the metal, then surrounds the crud, and leaves it suspended in the oil so that it does not abrade the metal.
On that stain on the buttstock, if its tacky, as you describe, I suspect someone has allowed some kind of alcohol based solvent to contact the stock at that point, and the finish has been partially dissolved. That is unfortunate, because the solvents may also now be down in the wood fibers too. Chuck Dixon can take a good look at this, tell you the extent of the problem, if there is one, and fix it, or tell you how to fix it.
Congratulations on owning a fine, old, original gun. Oh, that barrel is made of IRON, not steel, so be nice to it. :thumbsup: