look over what everyone else posted. did you take of the transmission cover? if not, and it didn't leak before, start from there. if you took the cover off, and now it leaks, then you may have assembled it incorrectly. check the paper gasket and be sure all the seals are tight tight tight. you can replace the screw you mentioned easily enough, if you can get it to come out (i'm sure someone can give you directions on how to do that). good luck.