It's not the easiest of jobs...but it's possible.
There are a few ways of doing it, but here's how I did one on a 156 recently (give or take):
Remove battery, air pipes, throttle body, thermostat, water pipes to improve access.
Disconnect clutch pipe and crimp to prevent fluid loss/air in system
Jack/support car and remove wheels.
Support engine. Drop exhaust and remove rear engine mount
Unbolt 6x hex bolts/nylocks from driveshafts. Nylocks should be renewed on refitting. A long hex socket makes life easier.
Remove starter and earths from gearbox
Remove gear linkage cables. Removing the damper thing helps as well.
Unbolt gearbox from engine. Remove 2x studs from box above/below diff
Remove near-side mount.
Lower box and engine. When it's almost out, raising the engine a little bit helps things.
A lot of wiggling and rotating is required to get it past the subframe. It's probably easier to remove the subframe, but that's a pain in its own right.
Good luck with it