if you crack open the case, visually you should be able to see alot of the problems.
If i synchro spring is broken, it might have broken off or it might not hold that particular gear in.
You should be able to see a good amount of the teeth on the synchros and such.
If your going to pay someone else to crack it open, you may just want to have them pull it apart and go through the main and countershaft. That way, you can check all the bearings and such. If your just oing a tear down and rebuild, probably shouldnt take anyone thats done it more than 3 or 4 hours (if everything checks out)