Hi Tony,
The only thing to watch out for is the front left side chassis strut. In mine, it is about an inch too far back and so there is only a 2 mm clearance between it and the alternator. I understand that this has been fixed on subsequent chassis' (Craig is going to work out a fix for mine - probably re-welding the strut slightly further forward). So it shouldn't be a problem for you. Here is a picture which shows what I mean. It is taken from above the engine on the left side, looking down. The front of the car is to the left of the shot and the alternator is right in the middle - you can see there is almost no gap between it and the chassis strut.
I didn't fit the engine, gearbox and diff myself, Neil Streeting did this for me. The hard part, as I understand it, is in fitting the diff. One of the guys at Craig's factory told me the trick to doing this (you need to remove a bolt in the diff and then roll the diff in), but this is covered in the manual so you should be okay.
One thing you might want to consider is adding an ABS system, which will require a separate brake line to run to the rear. I'm going to do this soon and it will be trickier now that the engine and transmission are in. If you are thinking about doing this, doing so before the engine goes in will be the way to go.
Hope this helps.
Cheers,
Richard