Don't worry about the door clips. Here's my source...........................
http://www.clipsandfasteners.com/GM_Push_Type_Retainer_p/a18353.htm
With a little research, I've found almost EVERY clip needed for everything from jeeps to imports on that site. Without the dealer pricing. Box of 50 for $11 break all you want.
I did the 4 beam high beam mod on mine (99 Tahoe) and it works great. I used a factory underdash brake controller harness for a 99+ truck, took it apart and inserted the wires into a blank relay spot in my fuse box. Added on fuse holder and tied the wires into the headlight harness right next to the fuse box. Looks COMPLETELY factory, uses a factory relay and works great. It took a little work getting into the fuse box, and a little planning to get everything right the first try. I can't be happier. I removed the factory DRL modual as I hate DRL's. I also went with an Alpine radio with Bluetooth phone interface. I disconnected the rear most speakers and removed the little BS underdash amp for them. Cut it up and used the plug from the amp to loop the back seat door speakers correctly to the radio. After the oil change make sure you change the fuel filter. Also, if you want the fuel pump to really last you, try to keep at least half a tank of fuel or more in it to keep it cool. If your A/C starts not switching floor/dash/vents, don't sweat it. The links are most likely gummed up, right above the gas pedal is the actuator. The little white arms with springs need to be cleaned and then lubed with silicon spray lube.
That's about it off the top of my head, I'm sure there is more rattling around up in my head.