It sounds like you have lodging and diving set up. Once you're on the dive boat you won't have a lot of say in where you go. The captain and DMs will make the decision but may ask your preferences. In my opinion there really are no bad dive sites in Cozumel. Haven't done the C53 so can't comment. Look for the restaurant thread on the Cozumel forum for good info on where to eat. Barracuda is a great location to walk to good restaurants. The further you get away from the ocean the better the prices and, often, the better the food (again, IMO). Rock N Java will be a stone's throw, on the same side of the road as Barracuda, and they have really good carrot cake - and Smash Box for burgers is right next door and has great, inexpensive burgers and fries. Jeanie's (attached to Barracuda I think) is hit or miss. The last couple of times we were there were misses, but others seem to still really like them.
The water will be chilly (80 degrees at the end of last January) so bring neoprene, and a boatcoat for surface intervals. It's a beautiful time of year there. You'll have fun!