Transmission Synchros
According to my maintenance schedule, the transmission FLUID should be changed at 30K, 60K, etc., not the synchros. Replacing synchros is only done when there is a problem, and is a major job. You have to remove the engine/transmission as a unit, then separate the two pieces. Once you have the transmission on the workbench, the rebuilding process is not that hard, assuming you've done other manual transmissions. You do need a couple of special tools, called ring nut sockets, to disassemble the transmission. There are three shift forks, one for reverse and first, one for second and third, and one for fourth and fifth. The synchronizer rings, or blocker rings, are over $500 each from Ferrari, although GT Car Parts here in Phoenix can get them for $257. Bearings are proprietary, and are hundreds of dollars each. I can't even imagine what gears or the synchronizers themselves cost. Still interested in doing the job?
Before you freak out, I'd try one other thing first. There is a sleeved rubber bushing on the shifter shaft a couple of inches from where the shaft goes into the transmission. The rubber deteriorates and can keep the shifter from working properly. The bushing is about $20 and can be done in the car. It is a little tough to do because it it is located right above a non-removable frame piece. Might be worth the effort, though.
And before someone else suggests it, you might try some Red Line gear oil first. If the synchro really is bad, it won't help, but it's probably worth a try.
-Steve