this is the deal with the 5th gear pop. The 5th gear snap ring is trash (needs cryoing). It will become compressed and break over time. As this happens the 5th gear synchronizer hub (which is pressed on) becomes loose and this whole assembly begins to slide back and forth inside of the transmission case, causing the 5th synchro stopper to come in contact with the case. It begins to cut and burn it's way out. Quite nasty. Aluminuim shavings through out the trany. If that's the only thing you want to fix, it's not to bad of a job. The hardest part is getting the transmission in and out. Now once your in there you may wish to do a full rebuild (all of the baulk rings always). the areas to watch for would be "reverse main gear sleeve, 2nd gear bits, all of the bearings, 5th gear and syncro (of course) which also means a new updated input shaft at $142 (wholesale) and any other nasty parts. It's really a good idea to get any parts (never the baulk rings though) that are being replaced cryo treated. A good place to learn more is
www.onecryo.com in Orlando FL. There are tons of other bits to watch for and replace during a transmission rebuild. All in all I spent about $1,200 (wholesale) in parts. All the little pins, seals, gears, baulk rings, etc... add up. If you can find a low mileage trany, get it and have the case opened and have BOTH the 5th gear snap ring and stopper "cryoed" (couple bucks) then installed. You could install them if you know how to turn a torque wrench. It's not that hard. Just make sure you have the # ONE helper. "A factory shop manual"!!! Yummmm yummmm. This is the cheapest way to do it right. Any other questions feel free to e-mail.
BTW, Red Line is incredible.