From the pics, a good scuffing should allow you to paint directly. Understand that incompatible paints (between what is original and what you use) will dictate your success more than whether primer is used.
I'd suggest a good scuffing with 400-600 grit dry. Don't work it so much that you remove the base paint, but these parts may have a fairly hard coat on them and you'll need a good surface prepped for adhesion. Wipe with denatured alcohol then paint. (Avoid paint thinner after sanding).