Maybe.
Your covers are off; clean up under the rocker pedestals at #1 and #6 and see if there is a crack visible. Note that they aren't always visible, so you can only condemn heads this way. Common 2.9L cracks like to go RIGHT through the Ford emblem on the tops of the heads.
Other possibilities are condensation from very frequent short-distance driving, or leaks at the lower intake manifold (almost always, this results in burning coolant and perhaps oil as well, and the vehicle passes a leakdown test).
It's in principle also possible for the front cover to leak into the crankcase, but it's much more likely to leak to the outside.
FYI, I describe small leak condensation like you're seeing as "Vaseline." If you feel it, it feels like water.