Clean all traces of dirt/dust out, and re-grease the fork pivots and slider arm and smooth surfaces with high temperature grease.
You can centre the clutch without a centering tool, by sticking your finger in each equal third portion of the clutch inside these little gaps. If the gaps you feel to touching into the friction plate are equal for all 3, the clutch is in centre.
When you put the car back together after its all done, start the car back up first before putting all the battery and other rubbish back in the way, because you might need adjust the cable again as soon as you feel how the car is when you start it up.
If you have a lower control brace, it makes things tricky, but you can kind of use that as a pivot to sit the gearbox up on when you're putting the gearbox back in the car by yourself.
Replace the release bearing even if the existing one seems fine.
Have fun.