Manual transmission is, in my opinion, little easier to overhaul than engine. I always recommend people to use Japanese bearing kit(normally kit comes with all the seals. Since world’s best bearings are made by them. (Bullet trains, and so on) If the syncros are out of spec, I recomment you to replace all of them. If you buy a hand press, you can pretty much rebuilt the whole thing in few hours.
Measure synchro clearance to spec.
If you are swaping transmissions, clucth cylinder and throw-out bearing sleeve combination is essential.
Try not to damage or loose front counter bearing thrust sim, as it is no longer available.