Check to see if your main breaker, the one with the number 30 has tripped. It is in the WFCO electric panel that has both your 12 vdc and 120 vac. Try switching it off and on as sometimes when it trips it looks like it's still in the on position.
Once you do that plug in your shore power and check your plugs to see if you have ac power to them. If you don't, go to your RV repair service place. It may be something as simple as the plug breakers have also tripped, or it could be something more complicated, but it's safer to let someone who knows the system check it out.
If your battery is not properly charging, then you may have a bad converter board. There is an easy way to test it, but given your stated lack of knowledge of electrical stuff, that too should be checked by your service shop. It takes about 10 minutes to change the converter board, so it won't be outrageously expensive to have them fix it.
While you have your trailer in the shop, ask them to go through the basic operation of the ac and dc systems with you so you'll get a better idea of how things work. With your stated level of knowledge, it'd probably be better if you don't try to do much with the electric system yourself. Once you have a basic understanding, then simple repairs can be done safely.