Before jumping to any conclusions, you should find out what your truck thinks is wrong. Whenever the Check Engine light comes on, the computer stores one or more diagnostic trouble codes, or DTC's.
There's a computer connector under the dash on the driver's side commonly called an "OBD 2 port". This has been a standard connector since 1996, and handheld computers that plug into that port and read the code(s) are widely available.
You can probably take your truck to a local auto parts store, and they'll come outside and read your code(s) for free! They're hoping to sell you parts to fix whatever the problem is - that's why they do it. Once you have the code(s), you'll have a much better idea what's wrong.
Come back here and post the code or search for it, and you'll be able to get more specific help.