Throttle potentiometers

after a long absence due to foreign countries a big hello to everyone! Hope you all had a good time and survived Easter well!

I have a little problem with my pearl again:
After the winter break I wanted to treat my 3.6 V8 to a little sun again. Then the problem: first in the stand gas extremely low number of tours up to going out; while driving in the tour area of approx. 1500 to 2500 more often a wrinkle...

the error was then quickly identified thanks to this great forum; the throttle valve potentiometer will probably be...

now the question: should one rather leave the installation and the associated adjustment to the skilled person or can one also do this (as layman!) itself? Is the error displayed in a diagnosis?

It's also funny that the lower screw is missing, but the upper one still sticks to the colour seal... Furthermore, the upper screw is so fast that it is not even possible to think of a simple unscrewing...

I would be really grateful for your tips and tricks!

Summer greeting from Switzerland
Gregor