Turret oil leak

Last week replaced turret upper boot and filled with oil (it was bone dry). Noticed fresh gear oil on the drive. Re-opened turret to find most of it gone. Working with a mirror and torch it seems to me that the o-rings that seal the shifter tube are leaking. I've only recently bought the car and not done any transmission work on this model. Questions: Anyone done this job? What is the least amount of disassembly required to fix - does the exhaust have to come off? Is the gearbox easily removable without the bell housing? Can it be done on ramps or 4 stands