See the top of the page? Where it says SHOP ONLINE. Go there and search for SHIFTER & LINKAGE KIT. There are 2 x types: bench and buckets.
Changing the box out is a piece of cake. Once the shifter is unbolted (which you probably will have to do anyway) simply:
Undo the bottom-most bolt that bolts the extension housing to the case. This drains the oil.
Remove the tailshaft.
Support the engine at the sump using a trolley jack and a piece of wood.
Remove the gearbox crossmember (2 x bolts either end and 2 at the gearbox).
Undo the set-screw that holds the speedo cable in and pull the speedo cable out of the box.
Pop the top gear pollution wire off the side cover.
Unbolt the 4 x bolts that bolt the box to the bellhousing.
Remove the box.
Only takes about 30 minutes once the shifter is out. Shifter unbolts at the top of the box through the hole in the floor. Linkages are just clipped onto the selectors on the box. Before you re-install a box with the new shifter, set it all up on the bench so that the rod trunnions are all in the right place on the shift rods - easier to do on the bench than under the car!
Make sure you inspect the clutch while the box is out, easier to do a clutch now that having to pull the box out again.
Installation is a reverse of the above. Check the gearbox rear rubber mount while it is out too. AND PUT NEW OIL IN THE BOX.
Here is a cheap rebuilt box on Ebay. These are exchange and you won't fix yours cheaper than this. A bearing kit is about $90 and normally you need at least a 1st gear (about $125), some synchros ($40 each) and often a cluster ($220) and an input shaft ($195).
http://www.ebay.com.au/i...ies&hash=item25736b8227