I can tell you now, that you will hate working at Gamestop. I worked at Gamestop for 5 years, started out as a part-timer and ended as an assistant manager. Once you make it to a management level you make decent money, but the job still sucks. You have to put up with a lot of shit and push the hell out of pre-orders and Edge cards. Of course you will make no commission on any of these sells. As a part-time employee you can also look forward to getting less than 12 hours a week on top of being paid minimum wage.
I always got a good laugh out of kids coming into Gamestop and asking for an application, then proceeding to go on about how awesome the job must be since we "played games all day".
The B&N discount may not exist anymore either. When I worked for the company they bought there share out from B&N to become there own company. So Gamestop no longer has any relation to it's former parent company, B&N. Also the discount at B&N, while better than what GS gives still was pretty shitty.
Also enjoy getting about $5 off new releases with that big 15% discount. The deals you find on CAG are almost always better than the GS discount.
One last thing, Gamestop does drug test. They usually only mandatory drug test management though. Passing a drug test is simple stuff though, assuming you smoke buds. The company is pretty lax on marijuana as long as you do your job and push what they tell you to and lie to customers about how they will never find a copy of Madden on launch day without having it pre-ordered.