As I understand it the repair can be made with the top left on. Assuming that the pins are sheared or stuck. Other repairs like a sheared pin in the linkage will require the top to be removed if the sheared pin is internal.
The left side (sitting on tractor) is where the different pin carrier is installed.
But if you need to get the actual differential out of the tractor then both sides and the top have to be removed.
That is the way I see the assembly anyway. I have never taken one apart in my life though.
As far as difficulty level, it is all in the upper half of easy to difficult. I would guess at 6-7 out of 10. The parts may be pretty heavy and gears can certainly pinch fingers hard. But if you use a wood lathe you are likely aware of that type of danger, I am pretty sure you could do it in an enclosed shed with a solid floor. I would NOT recommend doing it in a muddy field unless you built a wooden (heavy duty) floor and some tarp (tent) over the tractor to keep rain and snow out.
I still recommend getting the top off first to see what is going on - since the locking pins seem to be substantial AND you have not said anything about a loud popping sound when you applied the differential lock.
