Head gasket, intake manifold gasket or both?

I have a 1998 Ford Windstar with a 3.8L V6 that has 167k miles on it. Believe it or not, there has never been a problem with this van before other than a busted radiator hose.
A few weeks ago the engine overheated a little, still within normal limits, and I turned the heat on and got to the closest gas station and parked for a bit and refilled my coolant, no problems. A few days ago the van just didn't feel right, the temp was a little high, though still within normal limits and the engine just seem to lack some power so I pulled over. There was a poof of white smoke when I stopped and I popped the hood to see my oil was frothy and milky and I was leaking a small amount of oil from the passenger side of the engine. About 2-3 tbls. In all (that seemed like a lot when I was on the side of the road). I had it towed to my house and called four people, two mechanics and two car guys. Two of them say its a head gasket and two say intake manifold gasket. I say replace it all just don't kill me with a price.
Because of the age and milage one said I shouldn't even bother fixing it but it was the only thing my dad owned when he died and I can't get rid of it if it is fixable. Any ideas? Suggestions? The engine was never rough or loud or anything just lost some power.
Thanks