I had the bearings replaced in my gearbox last month. A place in Halifax did it for me.

From the top they removed the battery and battery tray, moved everything else at that level out of the way (ECU, cables etc.) and removed the selector gear. Then from underneath, obviously removed the under tray and protection from the passenger side inner wheel arch. There's a bar bolted to the side of the subframe and the inner wheel arch, that was removed. Then removed the subframe bolts on the passenger side and loosened the ones on the back of the subframe on the drivers side, but didn't fully remove them. Splitting the gearbox - removing the bolts holding the outer part of the gearbox (with the shafts and gears) with some careful levering on the subframe it moved the fraction it needed to to get the split part of the gearbox out of the way and onto the bench. The bell housing and clutch were not touched and remained in situ.

Then the magic started of removing the shafts and gears from the casing, splitting it all down into its components on the bench and giving it all a clean. Pressed out the old bearings, cleaned the inside of the casing, press in new bearings, checking the shafts and selectors etc. putting it all back together. I cannot remember which two shafts it was, but 2 have to be put and held in place together before the third would go in the casing. With some fresh sealer applied, the casing and gears were offered up and jiggled back into place, all bolted up and refit all the bits removed. Fresh oil in there (a little more than usual) followed by a quick test run check and all was done in 3 hours.

I know this is not the best description to be doing the job from, but that's what I remember. I'll be honest, I don't think I would be confident to do it, even having watched it all. Least of all having access to decent presses for the bearings. That's why I was happy to find them and the method they'd worked out to do the job, only removing what was necessary to make just enough space, having everything they needed sat on their shelf and happy to pay for their knowledge.

 

I had the bearings replaced in my gearbox...
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Excellent info thanks.
Not planning to refurb the box ourselves. My son's car so keeping cost to minimum by removing/reinstalling either paying to refurb or buying a replacement.
Hence question re compatibility of other M32 boxes in GM cars (Vauxhall and maybe Saab?)

 

I guess with some patience you could remove the 'split gearbox' with gears and take it to have the bearings pressed out/in. They did mine on a car lift so they had plenty of spece to get round it to get the split box out from the subframe. It might well be possible to do it if you are on axle stands on a driveway (etc.). I guess the only corner you might back yourself into is if you are supporting on the subframe as it's that that needs to move a fraction to make the space.

If it's any peace of mind, they were not so concerned how bad it sounded before they started - their replacement bearings would sort it all out. They were even prepared in case the the bearings were introducing some lateral shaft movement that can score a part on one of the 1st gear shaft (common) - they replaced that part. That stops the gear lever movement in 1st and 2nd. Mine wasn't the worst they'd seen and brought back to life. In the week I had to wait between booking it in and getting the job done, I was advised to drive steady as they could not fix it if a bearing exploded and took a chunk out of the casing!

I'm sorry that I cannot comment on cross model compatability as I never travelled that route. The only comment the lads made is that to get a 159 gearbox out Alfa fit a few more bits around the gearbox to remove that Vauxhall do.