yeah, they should be, i looked into rebuilding mine, i got quoted 375 for the synchros and stuff, and the same for the bearings, interlocks and detents, roll pins etc.... basically everything to rebuild it except the gears, shafts, shift rails, forks and housing.
About 800 for everything to make it a new box, but that was through a guy i know through work. so i reckon about a 1000bucks for everything or 500 for a minor rebuild, depending on whats stuffed and what need to be replaced.
but if you want a box to take a bit morre of a beating i would recommend loking a a r33 gts-t box conversion.
Soon to be back on the road, Turbo VG.