Sandi, AutoZone won't have a problem putting batteries back in! I think most auto part stores will do that for you.
I understand your concern about knowing how to connect and disconnect. I got a lot of use out of YouTube last month when my truck batteries died at the rv park. I have always been afraid to mess with batteries knowing you have to disconnect and connect in a certain order. Not really a big deal once you figure it out. My brother on the phone helped, too. After not getting them to charge, I had to remove both from under the hood of the truck and then put the new ones in. Yes, they are heavy! Where are the helpful, strong guys when you need them?
The only thing I can say about the Voltmeter is did you try it elsewhere and did you have it on the right setting? That's another one of those things I have to research unless it's for an electrical outlet.
I know it's frustrating, but it will get fixed one way or another so hang in there!!