Disney Quest is on the West Side of DTD. They have 2 food courts but only one of them is approved for the dining plan.
The main thing I remember them having for snacks was some pastries and cupcakes but you can look up the menu for food quest on allears and it tells you everything they have. You can get actual combo meals there like a hot dog or burger.
Disney Quest is right next to the Cirque Du Soleil theater and right across the sidewalk from House of Blues restaurant.
I see from your sig you have stayed at POR and OKW. If you take the boat from either of those places over to DTD it is going to let you off on the Marketplace side of Disney Quest which is at the opposite end that Disney Quest is on. I am not sure if they have a water taxi that takes you from Marketplace side to West side. I never investigated to see if they did. When we went to the West Side we drove ourself. When we went to the Marketplace side we took the boat.