I did this not to long ago. DO NOT USE the plastic/rubber rock shields. As stated they trap dirt, and cause rust on the outside, mine rusted through. Go here, this may help
If it gets cold where you are, the diesels had a pickup sock with a relief valve for when the fuel gels up. You're going to want that. I don't know the part number offhand, but I'll see if I have one at the shop so I can get a picture for you.
www.gmsquarebody.com
Start on page 6 post 87, shows the replacement and wiring, on a six wire system, six port valve. Do you have a switch in the cab?