In 2016, I blew mine driving along the freeway home, 110kph, no towing and minimal on-board load. Zero warning, just went bang.

Trying to source a repairer, there only appear to be 2-3 places in Sydney that will touch these boxes (I suspect due to weight and pain in the a*** value in getting them out) and that get recommendations for the repair from other people.

$600 in labour to remove/install.
$2300 approx for bearings/seals/new shaft & gear (and labour to do the work). Uprated gear (so better than the proper replacement, probably from Marks) was going to cost another $1200 on top of that. I got two of my synchros done, should've done the lot, my first now pops out occasionally when crawling down hills, but for now I've just taken to being a bit kinder to it.
$100 to get it towed half way across Sydney.

I thought about dropping in a wrecker box, but the question would always be over my head as to when that one was going to blow as well. The zero warning and then possibility of having to drive 100's of k's with 4 gears and the sound of metal trashing everything inside the box that was still ok dissuaded me from the idea.

Also came with I think a 20k/1 year warranty. Either way, better than if I'd stuffed around with it.