Coolant leak

My '91 KDX200 recently developed a coolant leak into the transmission. I've been looking through the service manual and it appears to me like there are a couple different gaskets/seals that could be causing the problem. Does anyone have any good ideas on which might be the most likely culprit? I will call the local dealer/service shop, but thought I might as well plumb the waters here too. Don't much like the thought of my gears grinding on water!

Thanks for any help,

David