Had to change tank on mine, the end of sun roof drain pipe wasn't in the sill properly and was touching the tank so water from drain instead of just dripping down was up against the tank and rotted it.
I charge mine through the 12s, so it should work just need to find which pins are permanent live and earth. On my 2004 there was a proper key hole on drivers door, when you get in better look up BMW door latch repair had to do it on mine.
Get the tank on eBay, lift up the panel round gear lever , to the right of lever there is a pawl to lift up to move the lever, hand brake think there is a wire behind panel right side of boot to pull from memory.
Should be some info on here about this, I a Vellman kit on my 53 plate then swap it over to the 08 I have now, just need to connect it to the 3 wire plug right hand side in the rear.
At least at 61 you stand a chance of working all the way through the hand book, I was 76 last Monday so I've been on borrowed time for the last 6 years lol. Should you be worried, eerrr yes lol.