I just replaced the air dryer cartridge on my coach at 46,627 miles and oil seepage for who knows how long. I have to say that changing the cartridge was one of the fastest and easiest things I have ever done on this coach!
I was able to do everything standing and reaching in from the rear engine compartment door. Had I wiped the hydraulic reservoir and body / frame better I don't think I would have even gotten dirty - a FIRST when it comes to working on this thing.
You have to reach in and around the hydraulic reservoir but it did not require stretching or the normal gymnastics.
Probably took 15 minutes tops.
I don't know why they have you replace the four 15mm bolts as they certainly aren't stressed or subject to any significant heat, but I did.