leaking oil cooler

i have a 97 catera and we suspect the oil cooler is leaking because we have had oil get into the overflow tank, still have white smoke leaving the exhaust with white creamy gunk on the oil cap. i was wondering would this cause an oil leak and cause oil to run down the ps valve cover and get all over the exhaust manafold and create a dex-cool leak and cause that to mix with some oil and run down the back of the motor onto trans. mount (also thinking heater control valve has gone bad because heat sucks on both sides). we have had the valve cover gaskets replaced. I was wondering too if you could tell me exactly where the cooler is located.
Thanks.:banghead: