Jimmi,
Don't know how much you have worked on these trucks but those screws like many are usually rusted pretty well due to condensation. I remove a lot of trim and find it helpful to use PB Blaster where you can and always tighten just a bit before you try and loosen, if the head strips they can be a bear. Also if you have a tight one loosen or remove the rest and you can usually get the whole piece loose enough you can wiggle them a bit to help break the bond. That trim piece is not available anywhere but from another truck so take your time.
