Rebuilding could cost as much as the car is worth. Not sure what you paid for the car, but should have been around the 6K mark.
As fordem says, it is not normal, or common for these boxes to whine, so a s/hand box should be ok & will be a much cheaper option.
Or, just give it heaps in 1st & 2nd
so you don't spend long in those gears - might shorten it's life if it is a bearing, or last for ages, getting louder if it is a worn gear.
Rgs, Michael.