As the vast majority of Holden Cruzes sold were automatics, finding out information on the manual version is not so easy. But I have heard of a few cases of this model suffering transmission faults where the gearbox becomes jammed in gear (and won’t come out) or jammed in neutral (and won’t select a gear).
If that’s the case, then it could be a case of a broken or faulty gear-selector cable or mechanism and may not mean the entire gearbox is toast. Either way, I’d expect more than 120,000km of service in a modern car before the gearbox died. But you haven’t told me the symptoms, so it’s hard to know what’s going on. Is the clutch okay? Is it a case of the driveshaft (rather than the gearbox itself) having failed?
As for replacing the gearbox with a brand-new one, I think that finding a good used unit from a wrecking yard would be a much more wallet-friendly exercise. The exception would be if the problem affected all manual Cruzes, at which point, a second-hand replacement would only be postponing the inevitable for a second time. But since the value of the car wouldn’t be more than the cost of a brand-new transmission, the equation comes down to whether you like the car enough to keep it. Is the rest of the car in good condition? If not, you might be better cutting your losses and finding something newer and with plenty of life left in it.