Yes and yes.

If you pull the small connector you should see the relay connector pin numbers on the relay. The connector will come apart and you can remove the harness wire from #31 and repace it with a new wire going into the cabin. In the cabin it connects to one side of a 'normally open' spst switch. The other side of the switch will connect to a nearby ground.
Ideally you should use a momentary pushbutton switch you will have to hold closed and there is no chance of leaving it in the "on" position.

If/When you get a replacement relay it should be easy to put back to the original configuration.