First let me congratulate you for this undertaking. Do you have any mechanical aptitude?
Do you own a basic tool kit? Do you own a voltmeter? (lots of how to on the web)
Youtube has lots of DIY videos on car repair. Get yourself a manual, Haynes is pretty decent. Look for used on ebay, etc. Don't run to the dealer for every little part. rockauto.com and others have competitive prices.
1. Look in your owners manual where all the fuses are located.
2. When you rotate the dimmer switch to on, it overrides the overhead switch. Probably bad dimmer switch.
3. If neither mirror operates. It's more than likely the switch rather than both mirror motors are bad.
When you post questions. Give year, make, model, engine size etc. The more details the better.
Alot of auto diagnosis is not "what part is bad", but rather "what is working". Then use process of elimination. If you don't, you'll wind up just throwing parts at the probably with no guarantee it will fix it. Lots of auto parts stores do have some experienced mechanics who for one reason or another just don't work on cars anymore. Others there "have an alarm clock, show up to work on time and able to pass a drug test"...
Oh, one more thing. If you post a problem. And one of the smart guys/gals ask a question. Please respond to what they ask, it helps with diagnosing.