theres 2 box's fitted to the 1.9 diesels,
the f40 and the m32
it will be the m32 fitted to this(later 1's are all these i think)
but its only ever the m32 that goes tits up,
and when they do they usualy blow a hole out the side of the box(but not always)
the m32 is also fitted to vectra c's, astra h's, insignia's and of course the zafira's
i look after a fleet of taxi's that use that box and its not unusual for this to happen
we usually convert them over to the f40 gearbox now as they're pretty much bullet proof(seen plenty with 300k+ and no probs)
this is usualy a cheaper alternative with vectra's as the box is cheaper but you also need to swap the driveshafts mounts and clutch so this might not be poss with the zafira
as for clutch and flywheel try get a luk clutch and dual mass,
this is all we fit and the last well in taxi's so must be decent