Well, a lot of people are thrown for a loop on the P99 mag release initially. HK handguns use similiar mag releases. The trick is to use your trigger finger. Don't try to use your thumb, like on a traditional mag release.
As for the gun show - it really kinda depends on your area and the size of the show. Tiny gun shows suck. Here in Tx, the large ones have awesome deals on new guns. There is a local one that just plain sucks, though. I wanted my money back it was so bad.
So, I make the 90 min drive to the Houston shows. They are great.
Many others complain online about crappy gunshows all the time. So, you'll just have to go to one and see what its like in your area. It seems to be regional as to whether or not the shows are worth it or not.