Newbie: Best way to learn about your RV?

Thank you all for your replies! The previous owner was owner number 4 and only used the rig for 1 big trip and then parked it for 2 years before selling it. He did not know much of anything about the rig except how to plug it in and run the generator. I had the mechanics check everything and it's all good. Badly needed an alignment and new shocks and tires but other than that it was good! (Didn't buy the tires yet -- recommendations??) I turned on the propane and ran the stove, but couldn't get the frig to light (how many times do you keep pushing the ignitor before you decide it doesn't work?). I turned on the generator and ran the AC and the microwave. The water in the rig had been drained so couldn't check anything water related. I can't figure out how to fill the water (although finally did find the hole in the door jam of the back door). I want to sanitize the tank and lines but can't find how to do it in that model year, and know I'm going to have fits trying to figure out the hot water tank once I get water flowing. Mainly it's just a feeling of insecurity in not knowing how to do everything yet and feel frustrated. And YES, I totally got a good lesson on NOT using that RV place! They basically just wanted me to drop it off and pay them for the work and weren't interested in me knowing how to do things for myself. No thanks.

Thank you all for your suggestions!
Linda