I bought 2 new gears on eBay and replaced both sides. They came in a set. I think you can buy metal gears but I figured Porsche made them plastic as sort of a weak link to start with the videos I found just by googling replacing boxster top transmission or something like that. It’s been a while and I turn 63 tomorrow so I don’t recall details like I once did
. It’s not that bad of a job. The 101 project book does a pretty good job of describing how to remove replace and time the transmissions. The video I found was about taking them apart and putting them back together.