We often do not know what level of experience you will have, so to avoid missing some critical points, I sometimes assume the poster has very little !
Not meaning to tell you things you already know but not wanting to skip things that you need! Sorry, if it sounds like I'm treating you as a rookie when you already know lots about the RV game?
But the first point is to get the idea of RV being two separate parts and those parts may not all have the same year!
The truck parts are what we find on most any truck, then the RV parts that Winnebago builds on top may be called a later year! Big idea is that we need to know what year when we go to buy truck parts and it may be different from the RV parts!
Before buying parts like spark plugs, be sure it is for the right year! This can be found on a label on the driver's left side (if still there!) or in the chassis manual if you have it.
This will get you to the RV manual which tells how to read the label:
https://www.winnebago.com/Files/File...8Chieftain.pdf
Down about page 11 is the dope on the label and what it can tell you.
Click this snip to see better or go direct for the full story!
There may also be a label out under the "hood" that has lots of engine info on it!
So starting, we need three things! Fire from plugs, fuel and air! Air is easy and we don't need to worry about the filter as it will run without a filter. It just keeps things like bugs out of the engine!
I think this might be a carb engine, so checking fuel can be as simple as looking down the carb as somebody pumps the pedal. Don't do this with key on as any backfire can go right into your face!
If you have fuel and air, check for fire at the plugs. Taking one out and holding it so it is grounded on the engine to look for spark as somebody cranks it, is one way to do a quick check without tools. I might use a pair of channel locks to keep my fingers back!
Hope that gives you some ideas that help get it going. Lots of small points after that may cause it so not run well but these three will often at least get it to try to fire and maybe start!