It would involve a hell of a lot of work!
New CUSTOM engine mounts, extensive welding, making your own parts

and to get it running with the exisitng controls and dials would be virtually impossible, you'd need to add a new dash and wiring loom.
Have a look in the Dub section, particularly Dizzie's car. He's got a 3 door with an Audi 1.8 or 2.0 Turbo engine under the bonnet.
I'd also expect to pay around 2-3 thousand, maybe more! Unless you've already got the lump!