Well, I pulled a few fender clips and one screw to access the bulb but I did not actualy remove the fender, the bottles were easy enough to take out, just make sure the truck is not hot when you go to remove the overflow
I'd go with industrial strength velcro for the location under the bottles, and 3M tape if you use the little shelf near the headlight (I used velcro there too but the glue isn't holding like the 3M tape would have) Under the bottles I'm not nearly as worried as it does not have anywhere to fall even if the velcro lets go but velcro make them more removable). Not sure what the other guy did that involves removing the headlights and grill. I know I sent one of my ballasts back for replacement when I first got them due to a slow startup in one with one bulb, and I would have been pissed if I would have had to remove the front of the truck to get to the ballast.
But I'm using the stock headlights, if you have to replace the headlight I think you have to remove the front grill anyways.