Ah good Jasus!
Verfeil, the Twin Spark (TS) is a different gearbox as Bob pointed out. Just for clarification, it will not go into a boxer engined car. The TS engine appeared in the 145/146 in 1997, so anything before this will be a boxer alright (again, as Bob correctly pointed out).
The 1.6 (8v) boxer and the 1.7 (16v) use the same gearbox.
Now, doing a boxer gearbox is quite simple... but takes a lot of time.
I would recommend that you replace the clutch plate, bearing and friction plate at the same time!!!
I will assume you have some experience with working on cars...? You will need two people I think...
You can remove it one of two ways...
1. Remove engine, then remove gearbox.
2. Remove gearbox by dropping engine.
Number 2 is the easiset.
You need to jack up the front of the car and support it very well!
Remove the plenum (air intake on the block). Write down where the hoses go!
Remove the flat bar running under the engine (I can't remember the name of it) and then remove the exhaust manifold. Disconnect the anti-roll bar too.
Take off the dust cover that hides the clutch plate under the engine.
Undo the drive shafts, be very carefull with this as it is easy to damage the bolts with an allen key.
Loosen the rear mount of the gearbox, this can be tricky as there is not much space.
Disconnect the gear selectors by prising them off the ball-joints.
Loosen the engine frame bolts, there are 4 of them I think.
LOOSEN SLIGHTLY the 6 bolts retaining the gearbox to the engine block.
Disconnect the reverse-selector light connection wire.
This part is important....
*Support the gearbox with a trolly jack.* Disconnect the rear gearbox mount.
Remove the two bolts at the rear of the engine frame to allow the engine to tilt backwards.
Then undo the rear mount support it on the trolly jack.
Drop the trolly jack a small amount and undo the gearbox mounts holding it to the engine frame. Disconnect the bolts to the engine.
The gearbox SHOULD roll out from under the car!
The replacement is the reverse of this.