Gearlinkage is piss easy to swap out, you will be using the one from a ABF mk3 or VR6 and the Gearbox from a VR6 too
Will also need the Clocks from a Golf VR6
The pedal box will probably be ok, its only the very early MK3's that don't have provisions on the pedal box for the Hydro parts
Id personally not go down the cable to hydro route on this application..
Would have been much better using a golf 3 VR6 as the donor, you can get them for as little as £500