I have 125,000 miles on my car and 1st gear is making a loud click click click while driving in 1st and goes away with clutch in. All other gears are ok with no noise. Thinking my 1st gear might just be worn or missing some teeth, how hard is it to replace just this gear? Would like to rebuild it while it was out but not having any luck finding a rebuild kit and not even sure what all I would need?