Helm,
The clutch last around 200 000km.
I am guessing that if this is the original clutch, there isn't much life left.
The clutch kit cost 299.00 Cdn + tax
The slave cylinder cost: 60.00 Cdn + tax
I would change the complete shifter linkage at the same time (all the wearing parts) and install a Z8 shifter if you plan on keeping the car.
A E28 flywheel might also be a good idea if you are into upgrades.
'85 Euro 635csi Race Turbo, megasquirt, Group A
'92 525i Touring 5 speed, 3.46 diff, UUC 8.5lb flywheel, soon to be turbo.
'02 Subaru WRX Wagon with STI springs, bigger sway bars