Head Gasket?
 

2002 4.6IS - 138,000KM

So i'm on my way back from the airport last week and she starts running very rough. SES light comes on. Just as I pull into the driveway, everything returns to normal. Temperatures were VERY mild.

This morning, temperature was -27C - with windchill -37c
I pulled into work, left it running outside for a minute while I ran into my office to grab something. When I came back out, SES light returned and it was billowing some serious white smoke out the butt end.
Smells clearly like oil burning.

Before I send her to the indy, what should I be checking for to have a general idea of what's going on?
I keep reading about this cold weather issue causing "cheese" at the oil cap. What else can i look for?

oil seperator.
another 2000 into the money pit X5