Hi There!
I'm new here.
Milky stuff on oil cap? Our 1988 Chevy truck has that problem a lot.
Yes it's anti-freeze. But going so far as to start pulling the heads off the engine right away is, shall we say, not a good idea.
First thing to do get an oil sample off to a lab. Auto parts stores sell these little kits for a couple of bucks. Find out what it is that your dealing with first. Yanking heads might be a lot of fun but expensive especially if you don't have to. Keep your car in one piece for as long as you can.
Get your cooling system pressure tested, or vacuum tested, whatever your mechanic prefers. What if you pull the heads and find nothing wrong? :WTF
Eliminate what could have happened first. water in the fuel, leaks in the intake manifold or some other source of water getting sucked in the engine. Who knows it maybe a bad radiator cap.
Happy Hunting!