Gunsmithing, even the basics is a hands-on skill. Unless you are already a machinist, check out what firearms are most popular and learn about them. Assembly, disassembly, tools needed, troubleshooting, etc. There are some good DVDs out there, but many skills are firearm specific. Knowing the Stoner variants, (AR-15 clones) is a good start. Being able to work on semi-auto pistols and bolt action rifles is good, too.
Thanks for the tips. If I do it, it will be a start from scratch proposition, but they say learning new stuff keeps Alzheimers away.LOL