I'm assuming you have a class A gasser, pretty simple job, takes less than 15 minutes on our Monaco with 8.1 on workhorse W24 chassis. Grab a wrench, even an adjustable will work, grab receptacle for used oil, your favorite oil and filter, maybe an oil filter wrench although I just use a rag to twist off filter, and have at it. As mentioned above most auto part stores or Walmart will have all parts and room in there parking lots, they will also recycle your old oil when you are done. Basically, if you are physically able, you can accomplish this task in a quarter hour, find a flat spot to park and get it done.
That is what I love about our class A, it is so easy to do maintenance work with all the space around and underneath powertrain, no need to jack up rig making service intervals on our Allison 2000 series tranny a breeze. It sounds like a few have had issues with spills which can occur but rare, a piece of cardboard or small tarp will alleviate any minor incidents. At 40' long and 13' high it is way too much hassle to find, and drive, and wait for our class A rig to be serviced by some junior mechanic doing this menial job at whatever service center that happens to actually work on your brand and chassis of rig.