This actually pertains to all trucks, not just the diesels. Your results may vary, but this is what I did.
Contact your local dealer with whom you have a good relationship with. Inquire with whom they use for body work or paint work, usually they will give you a name of a person to talk to with whom you can throw the dealers name at.
Call the recommended paint shop and ask for the individual whom the dealer recommended and mention so-n-so said you should call them. Inquire with the paint shop that your looking to purchase some Bushwacker fender flares and want to have them painted but would like to know of a 4wheelparts or similar that they obtain parts from. They will probably also provide you with a name with whom you should talk to.
Call the 4wheelparts shop or parts shop they recommend and ask for the individual whom the paint shop recommended and like above, mention so-n-so said you should call them. Chances are, because the paint shop deals with this parts center, you will get a pretty good price, or a better price then if you went there direct.
To make a long story short, I got a full set of OE Fender Flares, the ones that stick out about 1-1/2in, for $355 out the door. Buying them straight from 4WheelParts will run you about 455 +tax.
So the moral of this story...you never know unless you ask.