Had a similiar thing happen to me. I couldn't use first gear and when i took off in second it was making a winding noise! Sounded sick, in the end i couldn't even use second gear. So i decided to get a second hand gearbox from a Jap Spares Parts in Hobart for $450 with 3 months warranty. Put my car in the garage and decided to change it myself. It isn't hard at all, you just have to have a go. I did make a couple of minor mistakes though, when i got the old gearbox out i left the dowes in the old gearbox. Also i replaced the two main CV Shaft seals, but when i put the LEft Hand side CV Shaft in i pinched the seal and it is leaking a little now.
About 4 weeks later i had to replace the clutch, put in a PBR Heavy Duty cost me $370 installed ($270 for clutch and $100 to install with my help).
I am not completely happy with new gearbox as it is a little noisy when in neutral, bearings the mechanic told me! Anyways it is still going.
Nick