Most likely it needs a head gasket, you need to do a compression check and a leak down test to prove this.
At least the 4 cylinder is much easier job than the V6.
If you have an ATX, you also need to read up on the poor cooling of the transmission oil and there is only a metal screen filter not a standard particle filter to get the grit out of the oil.
So add a plate or parallel flow style oil cooler for the transmission. Tube on fin coolers are not as good as plate or the parallel flow cooler of the ford focus. I just bought one on Ebay that is meant for a Ford Focus and it looks like it will fit nicely right in front of the engine oil cooler. I am also thinking of an add on oil filter to insert in the line when I hook up the cooler.
