Need help about problem

Hey guys, wondering if you could help me figure out what the problem is.

Tonight, started up my 2000 v6 Mustang, and it started shaking.
Figured I'd wait till the car warmed up, but the shaking persisted.

When I got on the freeway, there was more shaking and power loss. The 'engine service soon' light started flashing
Took it to the gas station to fill up, and check my fluids, which was fine.

I'm thinking that I may need a tune-up or something?
To come to think of it, when I changed my spark plugs and wires, I didn't get to change my distributor cap.

Maybe that's the problem?
 
Have you double checked to make sure none of your plug wires got crossed up by mistake? If all of that is correct, then it sounds similar to the symptoms I experienced when my coil pack went bad.

As was said above, get the code read. Auto Zone does it for free.