Hi EWalton, welcome to Cruise-Chat! I think Dave has sailed on all of RCCL's ships, so if he says Oasis, I'd be booking it. From everything he reported when he sailed on her and other reviews I've read, she's one magnificent beauty. Oh, and by the way, she's HUGE!
The drinks (alcoholic) are priced about the same as a nice restaurant/bar in your area. Beer $3.50-$5.00, Wine $6 and up, non-call alchol $6 and up, call liquors $10 and up. I don't know of anywhere on-line you can find price lists, but as Cruise Fanatic states, there are lots of activities free of charge. Bottled water is $2.50 and up. The wi-fi is available, it is slow and expensive.
My personal preference is the southern Caribbean itinerary, but the Oasis doesn't go there. Please let us know what you decide.