No power

Getting ready to head South next week. After wintering motor home, left it plugged in and with all slides closed. When I went out today and opened the door, I could see microwave light on but nothing else would work.. Toggled battery connect switch but nothing comes on. Went ahead and started engin without difficulty and started generator but the only thing that would work is the microwave. I'm assuming I need to replace the batteries. We are not real handy at repairing things in the rv but surely we can replace the batteries. Any words of wisdom before we try it. We have an 08 fourwinds05 chateau citation. Can't get to the fuse box with the bedroom slide in. Thanks for any help you can give.