Hey Roger,
I put in the outlet that you are planning on my 3300SCR. As for the wiring, I could have tapped into the 110 outlet that is below the ice maker, but decided against that and instead ran some marine grade romex cable from the water resistant gasket covered outlet up to the electrical panel and tied into the GFI protected circuit of the Receptacle breaker. That way it is consistent with the nomenclature of the panel labeling. As far a accessing the area behind the outlet, I'm not sure on the 3000SCR configuration but on my 33 it was easy to get to by removing an access panel in the port side storage cabinet ceiling in the Aft cabin. From there it was a breeze to route through to the breaker panel. I cut the hole only after seeing what was behind the proposed location with a roto-zip tool and it left a perfect non-chipped hole. An old trick is to cover the area with duct tape to prevent any scratching of the gelcoat surrounding the the hole while cutting and viola' Done.
It is really handy to have the outlet in the cockpit. It's great for all different uses at the bar location; mixing up some tangy margaritas in the blender, vacuuming or powering a small space heater in the fall to just charging a cell phone. It also eliminates the trip hazard of running an extension cord from the kitchen outlet to the cockpit area.
Good luck with your project. Bella Sera 3300SCR / Jeff