Vanuber--Do you work on your VW and BMWs? If you maintain those, I think you will find most air cooled 911 maintenance is doable with a good tool kit, the Bentley manual, and the Pelican technical forum. There are lots of good videos up on youtube now as well (check out this channel for invaluable Bosch CIS fuel injection info:
https://youtu.be/slCzVrrST2Q ). I'd love to see pix of your R75/5 BMWs! I'm going to look at a /5 ('73 long wheelbase, with touring tank, same owner since '92) for a friend this morning as it turns out.