Removed the running boards and nerf bars from and 01 Yukon and 05 Tahoe this weekend. For anyone who run across this thread in the future here's what you need to know:
05 Tahoe: Easy, no instruction needed climb under there and unbolt
01 Yukon: Clear your afternoon plans.. You'll be working with 16 or so brackets, T40 star bolts, 10mm nuts/bolts and HVAC hoses and clamps. If you wanna see what it looks like without running boards first -> start with the drivers side as there's no HVAC to work with. Locate all of the T40 star bolts and carefully remove without stripping (if possible). If you strip any of the star bolts you'll be removing the 10mm nut/bolt combo between the running board and body. 1-10mm bolt on each side of the truck appeared to have been rounded (stripped) from factory as these were the last to touch these bolts. This involved having to drill through the fiberglass of the running board (around the bolt) in order to release the running board and shear the bolt. As for the HVAC hoses on the passenger side. The plastic hose clamps securing the hoses to the inside of the body are 'snap' apart from the middle of the clamp. Using a pliers, you can slide the tip of the pliers into the small holes on each side of the bracket and pry them open from the middle. Wear safety glasses and preferably keep your mouth closed, preparing from sand, small rocks and whatever else has collected behind these hoses. Good luck. On these older models it does look pretty clean without the runners.