Gas Cap Caused Two Week Downtime

I have a 2006 Suzuki XL7 that has been running pretty well since we bought it two years ago. A couple weeks ago the engine light came on and the engine started sputtering when stopping. Great, why does something always go wrong when we have camping planned and we need the truck. We just threw a birthday party for bot of my kids, so I was low on money. I told my wife I will get it fixed when I get paid next, two weeks away.
The truck sat in the driveway, un-driven and we continued our daily lives with just one vehicle. I hate to spend more than I need to for anything, so I searched the Internet for solutions. I was sure it was the spark plugs, but I needed a diagnostic test first. I looked under the hood and I am not really sure how to change the spark plugs on this thing. It is the first vehicle I have ever owned that wasn't self explanatory. Anyway, I wasn't sure since the vehicle has 43,000 miles and the spark plugs should last up to 100,000 miles and the oxygen sensors should last 70,000 or 80,000 miles. I finally came across a post that said if your gas cap is not on correctly, it will cause the engine light to come on and cause problems similar to what I had experienced. I thought this was a joke or something. It turns out the cap wasn't on correctly. I tightened the cap and reset the electrical and everything is working fine.
I am upset over this for a whole bunch of reasons. I could have fixed the problem for no cost. Who's idea is it that the gas cap will cause this kind of problem. He must be an idiot or a con artist. He's the same person that will charge you $300 at the dealer and all he did was tighten the gas cap.
The second reason is that here in Oregon we don't pump our own gas. I moved here from New Mexico and Michigan and i think this is the stupidest thing ever. Everybody here seems to think it's the greatest thing since sliced bread, everyone who has never been anywhere else. I spent more time waiting for someone to start pumping and putting the nozzle away that I would to do an entire fill on my own. On top of that, somebody else put the gas cap on for me. This is not acceptable. I have been screwed by people doing poor work on my vehicle in the past, but I thought I would never have to watch someone put gas in my car. I guess I have to double check everything myself. Unbelievable!