Well it depends what donor you go for and how spanner handy you are, don't whatever you do buy an Audi longitudinal engine and try and fit it into a mk2 as it is a royal pain in the batty,

A BAM or AGU etc is pretty straightforward to do main headaches are converting to a hydraulic clutch, getting the boost pipes run and wiring it in, you can go the qpenq route if you have the money to throw at it but altogether so far I have spent less than £700 doing mine it's been a ballache and the donor car was the wrong one but in effect I got my engine for free and have done everything myself work wise. All the bits and pieces I needed I have bought from classifieds or made, I could have spent a couple of grand and it would be somewhere near done by now.
I lost hope with it a bit but am about to go round to my garage and blitz it
