I did it with a small screwdriver (metal) for watches. Those plastic screwdrivers don’t fit well in the metal of the trimmer. After adjustment, do check if voltage is still ok because using a metal screw driver may influence the adjustment.
Question 1 is tricky.
It depends on your experience level.
Mine took about 24 to 36 hours.
This was over about 3 weekends with a lot of interruptions
You should really look at the build instructions http://www.k8200.eu/
Even after you build it there will be a lot of tweeking to do.