spanish phrases for a sales associate?

Hey all! I live in Albuquerque, New Mexico (though I am not a native; originally from the east coast) and I work at GameStop. Needless to say, we get a fair number of Spanish-speaking customers whose English is either very poor or nonexistent, and my store doesn't have anyone who speaks Spanish enough to help them much. I'm the closest thing we have to a Spanish-speaking associate, and I don't know much; I do speak a little Portuguese, though. I was wondering if I could ask any of you who speak Spanish (particularly Mexican Spanish, though I am not clear on the differences between the different regions of Spanish) for a few things.

I already know how to say basic stuff, like whether or not we have a game, the words for used and new, and how to warn for a couple of the things on an M-rated game (blood and violence), but it's really not much in the grand scheme of things. The following phrases I'm looking for in particular are:

"__% off..."
"educational game"
"discount"
"receipt"
"Would you like to reserve/preorder...?"
"Your change is..."
"Would you like a bag?"
"This game is rated ____ for ____."
The translations for the ESRB ratings; E for Everyone, E10+ for Everyone 10 and Up, T for Teen, M for Mature, Rating Pending
Some of the ESRB rating warnings: Sexual Content/Themes, Drug References, Nudity, Alcohol References, Fantasy/Cartoon Violence, Comic Mischief, Suggestive Themes, Strong Language, Mild Language, Blood and Gore, Intense Violence, Sexual Violence, Use of Drugs/Alcohol. (If you're not sure of the contextual meanings of any of these please let me know. More information is available on this page at respecttheratings.com.)

Thanks in advance! If I can get a good list of phrases together, I'll hand it over to my boss and we'll keep it behind the register so we can help more of our customers. I always feel so bad when we can't help someone because of a language barrier :\