Engine/gearbox swap isn't that hard. The ancillaries will probably be a bigger pain than the big stuff. I'd find out what is involved with the loom swap etc before attempting it at home.

Best know someone who is handy with tools and has all the right gear!

Although taking it into S-Technic would be easier, and you can always visit them daily with beer and baked goods and I'm sure they'd teach you a thing or two whilst doing the car!