Serious problem. HALP!?

So for a while, i've suspected my girlfriend of cheating. She goes out on "girl nights" every tuesdays and thursdays but I think she's been seeing a guy from work. Anyway, I decided to hide outside this last tuesday to see who drops her back off. So I hid behind my Harley and waited, right as I saw a car pull up I noticed that there was some fluid leaking from my transmission case. My question is, is this a repair I can do myself, or will I have to take it to a mechanic? Any help would be greatly appreciated.