I have one I have yet to install...
It is as simple as a lead and ground. I have a two wire that needs to be grounded.
One wire (black or red) to a 12 V source. Cig lighter, open jumper (stick a fuse in) and go straight to the fuse block.
As for install, if your hole is tight enough than you can seal with anything so long as it is rated for it. Granted a kit specific application would pretty things up and guarantee no leak, RTV sealer will work on mine.
I have to drill through and get around a snorkle, so The mounting kit won't work for me. But if anyone is interested, I will take pics and show my progress for anyone else to follow... that is when i get around to it