Hello mr.borrie,
yes i'm located in Germany.
Broken camshaft adjuster. Hm, the question is if there is other damage caused by that. How many Km does the car have on it? Don't buy a car you haven't seen and inspected in person.
The best books you can get for this car is the official Porsche workshop manual. There are also books from Bentley publishers and so on.
I think an universal OBD reader won't be the right decision. Better will be a Durametric diagnosis tool. An original PIWIS system will be to expensive. Maybe you should look for an independent Porsche workshop near you, that has Porsche diagnostic tools.
And don't forget it's a Porsche. So you're dealing with spare part prices that can be unpleasent. Especially if you need new Porsche OEM parts to fix problems. And don't forget, the car you're looking for is 19 years old. So there will be parts failing from time to time.
Regards, Markus