Transmission problem

[SS109]

Decided to go for an afternoon ride today. Well, I didn't even make it out of the staging area before things went wrong. Warmed it up properly and started to head out and my bike just died. It felt like it locked up. At first the shifter didn't feel like it wanted to move down. However, it moved upward and then it shifted fine. Did a slow kick to feel for any problems with the engine but it was smooth. So, I kicked it and it fired right up but could hear something like a knock. Cruised it up through the gears and 4th is making a noise like some teeth are missing.

Questions. I'm pretty sure something went South in the trans (duh) so I will be splitting the cases. Supposedly the engine is a '05 EC250. Can someone help me with making sure? The numbers on the engine is EC25 0104037183. Second, where do I find replacement parts? Since I'm in there I plan to rebuild the whole bottom end. Anything in particular to watch for or should be upgraded? Any other input on splitting the cases? I have rebuilt Japanese bikes before but never a GG.