I dug into a customers box last night and from the cursory inspection it was one of the cleanest, least abused gear boxes that I have ever been in (from a customer). Most stuff will need some changing around with very little parts replacement. There was no complaint that I know of. Once I removed 1st gear I saw this
Click to view attachment
Click to view attachment
This is a common cause of high gear whine. In the higher gears the pinion shaft, which is what the lower bearing in the intermediate plate pictured here supports, is spinning at its highest RPM. At this higher pinion RPM most problems with this part of the tranny will become evident. If you have a whine at lower gear and higher engine RPM then you most likely culprit is the input shaft bearing which is the upper bearing in the intermediate plate.