I have bought multiple copies of games from used stores and flea markets... Never had any problems...
I think the people around here are too damn stupid to counterfiet... Wouldn't suprise me...
Oh, and off topic,
TMC is tottally worth it. If worst comes to worst and you can't find it (And I say this as an utterlly last resort) emulate it. Emulate it, then donate like 50 bucks to Nintendo. o.O