Lately I've been having some noise while in 5th gear. There is a 'clacking' sound when I let off the gas, or am coasting. The shop thought it was a thrust washer for 5th gear, and suggested I replace the tranny fluid, put in some conditioner and go from there.
After draining the tranny I felt around in the drain hole and found

some gear teeth. I pulled a few out, took it and the fluid to my mechanic, who is now recommending pulling the tranny and sending it in for a rebuild. He is guessing total cost should be about $3000 in the worst case scenario, which I am expecting.
Right now I'm just looking for any suggestions, opinions, options, etc. regarding the rebuild. I don't know much about transmissions, so just looking for some advice. Is this an appropriate cost for a rebuild? Any recommended upgrades? My truck is pretty much stock, though I'd like to chip it someday with a little extra power, nothing extreme.