I think I've heard people say Mike (Ex-Gtir) can drop the engine in about 2 hours, splitting the engie and box, changing the clutch and putting it back together should then be fairly straight forward, So I'd be surprised if he can't do the whole thing in about 6hours (at a guess) with no problems. But he will be able to tell you the time.
Olly does it with the engine in and someone said he takes about 12hours, but again he will be able to confirm the time.
So looking at that it's alot easier to do it taking the engine out...
IF you have al the specialist tools necessary