96 ford taurus ticking noise???

I have a 96 ford taurus Lx 3.0L V6 DOHC, everything is working fine exept that there is a ticking noise coming from the engine i think. It sounds like the valves need adjustment, but i was told they are not adjustable. The noise goes away when i rev the engine up or when i shift from drive to parking it will stop for a while but then it comes back. oil level is good.I was checking my car and found some oil in between the two cylinder heads, it looks like a valve cover gasket is bad. Can anybody help. THANKS

While you've got the valve cover(s) off, check to see if one rockerarm is a little looser than the rest. You could very well have a collapsed valve lifter.

will that be hard to fix or expensive??

I don't think the part will set you back much. But I'm not familiar with the Duratech engine. Wander over to http://www.taurusclub.com and ask around - someone there will know.