Greetings - that's a very interesting choice of vocations!
There is a forum for collectors of the U.S.-made A.H Fox shotguns here:
http://www.foxcollectors.com/ah_fox/content/disassembly.html
The only reason I suggest joining and reading their forum is that the members are quite serious about their guns and are especially interested in the subject of restoration. One section of the forum is devoted entirely to that subject. I am sure you will find many ideas there as well as here.
I'll only comment on wood, as I have yet to tackle the metal on mine.
As wood ages, it loses its original oils due to exposure to the elements, gun cleaning fluids and just straight evaporation - a very slow but steady and insidious process. As it loses its oils it 1) shrinks and 2) becomes very brittle.
The shrinkage often causes looseness to develop in the metal to wood fittings. When you disassemble the piece you must be very aware of this and, as mentioned by an earlier poster, you must have a detailed plan of HOW to disassemble it, and you MUST have the correct tools. I can't stress the tools enough. For example, all of the screw heads used on antique firearms are of the 'slot' headed variety, and the slot heads made today (and hence the screwdrivers for them) are NOT necessarily the same size as the old ones. You may or may not know that slot head screws are the MOST prone to damage when used, and a messed up screw head will have a direct negative effect on the value of the piece when re-assembled.
You can purchase gunsmithing tools that will have a perfect fit for various components - including the above example of screwdrivers.
But do check out the Fox Forum, if for no other reason than to be inspired by the beautiful restorations shown there.
Cheers and good luck!