T680 battery access

I just got this truck and the 1800 watt inverter is not acting the way it should. If I run a string of Christmas tree lights it does just fine but if I try to run my 700 watt microwave it shuts off and then goes right back on. It does this every time I try to operate the microwave.I'm thinking it's a loose or corroded electrical connection. I'd like to check where the inverter is wired to the battery but I can't figure out how to Get access. It looks like there's some bolts holding on the side trim pieces where the steps are. do I have to remove those in order to get access to the underside and the battery? If not how do I get access to the battery.

 

Driver. Need to refi the house first, then buy a truck and go o/o.