Classic/Antique Car Repair: i have water in my oil, suburban 4x4, competent mechanic

Question
i own a 1999 chevy suburban 4x4 350 small block. i had my oil changed about 3 weeks ago. shortly after having it done i started loosing water but could find no leaks. so i then asked a friend about it and they checked my oil. it was about a quart and a half over the full mark. it kind of looks like melted chocolate. what do you think could have caused this and whatv do i need to do to fix it?

Answer
It sounds like the probability of a blown or leaking head gasket. It is time for a radiator pressure test and a test to see if carbon monoxide is getting into the radiator. In other words get it into a competent mechanic if you do not have the skills. Do not drive with this mixture in the crankcase as it will damage the bearings.
Brad