[Carl n Susan]

It will be pretty simple to add a 12V circuit to your 2955 (I had that exact rig once upon a time). As I recall the fuse panel is under the refer. You can tap in there and run the wires behind the cook top & sink area to the cabinet end near the door. That way the slow cooker can sit in the sink while traveling (more secure) and you don't have to try and mount an outlet in/on the vertical exterior wall.

As Ron said, check that you have enough battery to support the load required.