Originally Posted by dikzak

( I don't know if anyone is interested in this, but just for the sake of completing what I inquired about: )

I actually found a dealer closeby willing to get me the M5 and the E10 bolts for the valve cover and the breather covers. He wants 50 Euro for it, which is too much, but if that means I have the exact right bolts, I'm not bothered by the price.
Up until now I've replaced the following things in my car:
- Coolant and thermostat ( the thermostat turned out to be unnecessary, but whatever)
- Oil and oil filter ( most definitely necessary)
- Steering stabilizer ( definitely necessary and definitely worth the money and time)
- Belt, just because I didn't know how old it was
- Air filters ( also very much necessary)

Next up are all remaining fluids, the valve cover leaks, the spark plugs, the secondary air pump ( I found the thread in which the relais is pointed out as the culprit for the P0410 error) and anything else that I can find in the driveline that needs attention.
Then I'm gonna direct my attention towards the suspension ( some idiot installed springs on it that are way too low- the tires have almost rubbed through the metal of the wheel housing already) and the brakes, although they seem to be fine.
After that, there's still the matter of making it visually nice, and then I'm gonna need to get rid of some small rust spots and rustproof the rest of the car. Maybe look at some tuning ( replacing the exhaust, changing the throttle body to a larger one, maybe a chiptune) but that is for later.

So there's plenty still to do. On the other hand, all of the things I've done up until now are a first for me- I've never done any of them before on any car. So for now I'm happy with the way it's turning out. Even a tiny little bit proud, I might say. ( Mind you, I'm 24, I have no education or experience in this field whatsoever, I don't earn that much and I live in a country where cars are absolutely insanely expensive. So for me to be driving this car and to be able to make it at least somewhat better; I think I can be a little bit proud of that. )

Thanks for the help so far, everyone! I'll likely be back with more questions.