Have a look which gearbox your MK1 has.. if there is an under car gear linkage you have the older type known as the bottom shift, which requires a fair few parts to convert to MK2 (i've done the conversion but not driven yet)
If the selector mechanism travels through the car and through the bulkhead and enters the top of the box it's the topshift (oddly enough). If you have this type, then it's much easier to convert to MK2. the MK2 box usually uses hydraulic clutch but can be converted to cable if you swap the clutch arm over as the casting retains the cable bits.
I think it was e reg and before which have the older box, and I guess you have this box as they are prone to failure by all accounts.