I have just had 2 Fulvia gearboxes to rebuild as both presented xmas tree magnetic plugs on doing an oil change (one was my car and I knew it had a problem noise, the other a friends car that made no noise but has precious little syncromesh on1,2, or 3).My gearbox rear main shaft bearing cage had broken up but miraculously did no further damage. The other gearbox was a write off as 3rd was missing most of its teeth and1st and second where not much better. 4 synchro rings were less than min spec also.
I would say it is would be wise to pull the gearbox and split it....