I'm not really familiar with the disassembly, but I believe there are bearings on the drive shaft and it is held in from the backside. Remove the v-belt pulleys, then the bearing housing, and then there is some kind of taper-lock mechanism, as well as wiring. I'm pretty sure that the gearbox and shaft come out as one assembly. As far as the hydraulics, the machine must be powered down, unless you want to take a bath. I think you are correct about the turret mounting bolts in the center. But, I'm fairly certain that the turret side curvic coupling bolts in from the front side of the turret, and if there is only a small amount of error you can loosen the mounting screws to re-align.
Easiest method to get alignment is to make an alignment tool that fits inside the tool pocket with the tool holder out of the machine. The tool is bored on the end to fit over the live tool drive fork.
On the other hand if the turret is out alot, the curvic coupling may have skipped a tooth in which case you could unclamp manually and rotate back or use the tool encoder position to correct the index position. If you do need to remove the turret be very careful with the piston assembly when removing the turret, as scoring of this surface will result in leakage into the turret cavity during tool changes. I know the drawings leave alot to be desired. Hope this helps. Mikiemo