That depends. On mine, the rebuild and seal kits were about $500 total from Skidim. But that didn't include stuff like the needle bearings or any of the special tools to be able to service it (pullers and stuff referenced in the service manual). A rebuild on mine was $900 from Fantastic Finishes marine in Medina Ohio. You can ship a tranny UPS or Fedex ground. They turned it around in 3 business days. A new transmission would have been $1500 for mine. I got a crazy good deal on shipping through my work. If you have to get your tranny welded, then pay to have it rebuilt, and shipping, you're probably getting closer to the price of a new one, with easily 3 weeks of downtime.

I had a bitch of a time finding anyone that was willing to even touch a marine tranny.