Expect a crowd...you can't swing a dead cat around by the tail without hitting 10 people...

...no, seriously...you can't...
Most everything is negotiable, if you find something, don't be afraid to haggle...
As far as prices...meh...the stuff I'm interested in (mil-surp, ammo, accys) is nothing to write home about, but fair I suppose...again, haggle...
I'd be cautious about buying ammo at a show, some less than honest folks will sell crappy reloads in factory boxes for a "great deal"...
You'll see a metric azz-ton of poly frame handguns...lots of rifles...AR/AK platform is always popular, lots in that dept, tons of gadgets, gizmos, literature, preps and impulse buy stuff...not much for wheelguns sadly last time out but every show is different...
Grab some business cards and chew the fat with some vendors, I'm sure if what you're looking for isn't on the table, someone can give you a lead...
Get a pretzel, make sure to stop by the GRNC table and toss a couple of bucks into their donation bucket and have fun!!!