[oletrucks] priming new patch panels

[Tom Cooper <tntcoop@earthlink.net>]

I ordered some inner and outer cab corners for my truck. I also ordered a 24" 
door skin and both sides steps and rocker panels.
The cab corners are black but the door skin and steps are not. Do all these 
parts need priming or is the black coating a primer?
If i do need to prime, should i sand them with 180 before priming. Any advice 
is helpful and needed...
       
                      thanks  
                      tom