hey man. Age is not an issue. I am now 26 years old and I've been going to gun shows since about 5 with my Dad. Never, ever have I been carded at the gates of any gun show. Now a days I also bring my daughter along ( she loves em'). As far as Nagants. Thats where I bought mine. There is always about 80 to 100 nagants in any building there. May I suggest though, there is one guy who is a private collector of nagants, who will have 44's 38's 91/30's of all origin. Since they are his private collection he usually brings about thirty of em, and they are all graded by number from 1 to 10 on rarity, bore, stock condition, things like that. I hand picked my 38 from his lot, which he had rated a 9. I swear its the cleanest, nicest bore, and stock Nagant I have ever seen in person. I paid about 20 bucks more than from some of the other guys. But it is a friggin tack driver and beautiful to boot, all matching numbers, sling, and acc. kit also. I walked away down 135.00 with the utmost favorite rifle of my collection.
As far as AK stuff...You can't make it down an isle without tripping and falling dick first in a pile of AK stuff...so that won't be a problem..
Good luck, cuz you are making the right choice with a nagant. Accurate rifles and you just can't break em or shoot em out.