You have to check your level at normal temperature with the engine started and in the run position. Now you go through each of the gearing for 2-3 seconds between sections, not move it to the transmission NEUTRAL position and check the level.

If you check it like motor oil you are doing it wrong and it will appear to be too full, it has to be running and at normal operating temp and tested in neutral on a flat surface after you have gone between each and every gear to ensure there is no air bubbles. NOW YOU CHECK THE FLUID LEVEL.

 

Also, since it's a 2001, you can pull the codes yourself...

Get in your truck, put the key in the ignition, and cycle from the off position to the on position 3 times, the third time leave it in the on position. (when I say on, I don't mean start the truck)

Then your odometer will show you the codes. You can proceed to look them up here and get a better idea.