I really don't know the history.  It was the first change since I bought it a week ago.  I don't know what the guy ran in it.  The oil was definitely not like a milkshake, if you mean white and frothy.  Any recommendation as to what oil to run in the trans?  As for the symptoms you described for the crank seals, all I've got is a little smoke and nothing else.  Seems to run strong and smooth.  Haven't messed with the carb yet since it runs so well.  It's not like I'm looking for a problem (aka big repair job), I just want to make sure she's not about to blow!