Earlier versions of the ST220 had a 5-speed mtx75 'box if you get one of these it should be easier to fit, - you will need the ST220 loom, ECU, and locks, keys etc - if not there may be problems with the immobilisor - the AC and heating etc may be a problem

It would be a fair bit of work

It would be worth doing as the mk2 is lighter than the mk3 - otherwise you may as well just buy an ST220 - less hassle