Technical Gearbox woes...

[stiffy]

I have a 2003 Fiat Multipla 1.9 JTD, with just over 95000 miles on the clock and a full, Fiat Service History.
This evening, driving home from work, 5th gear jumped out and I could not re-select it. It felt like it was in gear, but no drive and a sickening grinding noise as if it wasn't fully selected.
I have always had a noticeable amount of movement in the gear-stick when accelerating and decelerating and assumed a worn engine-mount was to blame, but today just before 5th gear jumped out, the movement was at least 2 full inches back and forth!!
1st and 2nd developed a worrying whine and I noticed gearbox oil leaking too!
I limped home and took a closer look, hoping it to be a gear linkage that had come adrift, but I could not see anything!
I'm preparing myself for the worst case scenario - a replacement gearbox (unless anyone can advise me otherwise), so my question is this:
On the basis that the Fiat 1.9 JTD engine is used in a wide variety of other cars, such as other Fiat's, Alfa Romeo's and Saab's, will other gearboxes fit my Multipla?

 

[Brajal]

my 2001 105 JTD did the same, during a long trip the 5th started to jump out to neutral and i had to drive it back with my hand holding the gear handle .
This got worse later affecting all the shifting until one day it stayed locked on the 1st gear.

The gearbox was rebuilt some cogs and bearings where replaced. But it stills makes a very light grinding noise on the 5th or thats me that I never trusted that repair shop ...

 

[JTDman]

When i bought mine it had a gearbox problem that turned out to be the gearbox oil seal , i had that replaced as well as the bearings in the box and all has been well since.