Well, the official statement I read just said that it requires "original packaging", so manuals a probably not what they're checking for. Not a problem anymore because they don't make them, but in the past it would have caused me headache to ask about seeing a game and then have to turn it away because of no manual. I've got a new outlook from 8th gen forward - no manual, no problem.
Around my area (where there's no such thing as a locally owned game store) nothing beats a GS staffed by good people. The one I frequent, the guys know me & know I'm particular about my games. I found a complete Silent Hill: Shattered Memories for the Wii the other day and was very excited because I had been looking for it and no one in town had had it until now. But when the guy pulled the disk, he goes "uh-oh" and holds the printed side towards me to show me something. At first I didn't see anything, and I told him so, then he tilted the disk slightly - in the black part of the label someone had written a number with a black marker. 
I was sad that the game was a no-go, but that was a lot better than having someone just slap it in an envelope and leaving me to find out about it at home & have to return it.
What I'm saying is, while I do trade in some at BB because they often have higher values and my credit goes farther there with my GCU 20% off, I prefer to do business at GS because the people know me and are knowledgeable about games. I have even shopping at Wal-Mart, so I can't imagine I'll ever try to trade anything in there unless they have some kind of insane deal for doing so.
On the odd occasion, I'll buy a game from Walmart. You never know what will be picked over and what will be left to rot at a Walmart. Walmart is actually where I found a $20 copy of Fire Emblem for Wii a couple years ago, also where I found Fire Emblem Radiant Dawn for the same price. But then I notice they'll hold on to a copy of Mushroom Men at $50 going on 4 years the same store. Which is anothing thing about Walmart's games department, it's very YMMV. They do whatever they want, they don't all have the same pricing or stock.
Funny thing, last month I was picking up something there, and noticed they were giving out copies of their own video gaming mag called Walmart GameCenter, which actually featured previews, interviews, and game reviews of it's own. Also noticed they now have game reservation tickets behind the glass as well. I guess it's all a part of their new plan to break more into the games market.
Poor ole' Kmart tried to do something like this a couple years back, but when corporate found the business as a whole was still hemorrhaging money in Q4 of 2011, they shut down the guy in charge of the "Kmart Gamer" program. He was a nice guy, he posted and kept in touch with the CAG forums a lot when drawing up his deal plans. They were doing weekly sales on different games, lots of new release incentives and stuff. It was short lived, but nice while it lasted.
