If you have the correct manual with all the info and being able to take things apart and put them back together again, you should be OK. Mark and clean all the parts you will reuse.
Replace all the syncronizers and front and rear bearings. Sometimes the shifting forks will be worn enough to replace also. Clean and check all the parts well. You may need a magnifing glass to see all the worn areas and sometimes things are worn that look like they cam from the factory like that. For me, it takes longer to R & R the tranny than to overhaul it.
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