New to Audi A4 life (but know the pain of the Audi classic cars)

Good morning, I just thought id introduce myself to everyone, as im the inept spanner monkey (as my partner calls me) who will be looking after the car below, my partner has just bought an Audi A4 convertible 2lt tdi 76k. Timing belt done at 52k, and a new turbo (Garett) at 65k.

Having never owned an A4 or a convertible for that matter im interested in what to expect, and what to look out for during her time with the car....

Im fairly confident with the spanners, and more than willing to get under the bonnet ect especially if it saves me from another trip to the dealerships.

Some of the things I know need doing are, the brake pad light keeps coming on, on the dash, previous owner told us it was a broken wire,(you can clearly see it has new pads and discs all round). The black roof has some green and brown stains, that look like its ben parked under a tree, how do I go about removing or reducing the appearance of these without ruining the hood? Then what should I do for some TLC to the hood, like reproofing it, cleaning it ect?

And one last thing, common im told to all Audis is the reverse parking module is missing, removed im told as it broke, So I clearly need one of these but have no part number or model reference, im sure it wont only be in the A4 convertible....im assuming its in all A4's maybe A3's or A5's, hopefully someone on the community can help me out.

Thanks for your time and hopefully I glean some useful tips reading the forum as I have done with my classic Audi.

Tiprat.