I've been changing the oil in all of my many and varied vehicles since I bought my first car (a 64 MG 1100). My coach is a FRED, made before they coined the name. It has a 5.9 Cummins so it only requires a 2 1/2 gallon container to hold the oil from the pan and filter, and I have only one fuel/water seperator filter to change. My engine requires that the oil be changed every 5k miles, so I have to do it more often than the larger engines. The shops would still charge me the same for an oil change as the larger class A's so it never goes to a shop for maintenance. I replaced my tranny last year (myself) with an Allison reman AT 545 (upgraded from the 542), this year due to a timing problem on my original 5.9 I had to either overhaul it or put in a new one, so I replaced it (myself) with another upgrade, went from the 160HP engine to the 230HP engine with a wastegated turbo and I also installed an intercooler which it didn't have. I had cranked up the fuel delivery and installed propane injection on the old engine, and was pushing around 220 HP with it, but I had to watch the EGT like a hawk to keep it away from 1250 deg. F.
Anyway, I'm not afraide of doing my own work, and I've saved several thousand dollars doing it.