Nice three part series on splitting the cases. Very straight forward and easy to follow.
https://m.youtube.com/watch?v=kYX-bOG9vR4
For much more detail then go to this link, scroll down to 1993 CR 250- Completed, then click each of the nine link sections for rebuilding CR 250 engine. This is Dogger 315?s build and it is much more detailed than a Honda factory manual with several tips and tricks. The basics will apply to your Gasser, I have a 2011 too.
http://www.allthingsmoto.com/forums/...n-index-53651/
Ok, once you have your transmission out, you should be able identify which parts are damaged. The trickier part will be trying to determine why they are damaged. If you post pictures here, then we should be able to help you determine the cause of the failure.