With most of these 'clip into place' things you can 'loosen' them off a bit from the other part quite easily.
Do this all the way round gradually and it should come off.
Yes on one side you can see that it clips into the other side so I think you should be able to separate them by using a sharp knife or small flat head screwdriver.
I would say it would need to be equal.And I would agree with some other people that servo motors and m motors are probably not the best thing to use.But rather XL motors and S motors to keep the price down.
I never did any thing other than mod the tires to mine......
And I have not done anything to my unimog ether than motorize it.
My simple mod to fit double tires.
Since four years old......I am now 22 and still buying what you see above is only my technic collection. I have a few tubs of the regular stuff as well.
You do not need the valve block, as your rams have both top and bottom ports to them.
I also think the size of the bed is ok.It is the chassis that needs to be made longer.
Welcome to Eurobricks it looks good for a first moc.
Two suggestions:
1) Move the rear wheels back more.
2) Move that other switch to were the other one is behind the cab.