[98 XLT 3.0 4x4]

I'm hoping you guys can help me out. When I let my Ranger idle for longer than maybe 10 minutes, it starts to shake, and keeps on shaking while I'm driving. More specifically when I get up to 50-55, it gets real bad. And all throughout that trip, until I turn it off and let it sit for a few hours.

Or if I crank it again shortly after I've already driven it (without any issues), the aforementioned issues start. Shakes real bad when idling and driving.

I recently changed out the spark plugs, spark plug wires, fuel filter, and air filter, hoping that any of these would solve the problem, to no avail. My check engine light has been on for awhile now, if that helps any.

Any suggestions/ideas? Or am I better off taking it to a Ford dealership and having them run a diagnostic?