Here is what I do know:

The 3.0 L inline six indeed is an overhead cam engine. However, the valves and lifters are easily accessible with the valve cover off. You don't even have to fool with the camshaft - simply work on the corresponding arm/lifter.

Looks like you have a V6 or V8? Apparently, the cams are a different setup.

As far as a stethoscope, I usually get by with either a long stemmed funnel or a screwdriver.