Repo, there should be a black rocker switch on the water heater unit itself, behind the panel on the outside of the rig. It may have a cotter pin holding it in the Off position. You'll need to turn that switch on. We leave that one on all the time and use the breaker inside the rig as the on/off switch. One thing to remember is do NOT turn that electric element on without water in the water heater. That will burn out that element in a few seconds. You can buy a replacement at a hardware store, if necessary.
As for the inside switch, we had a 2001 2880RL, which was the smaller version of your 3280RL. I do not recall such a switch in it. There is a switch in the inside that turns on the gas heater for the water heater. Maybe that's what they're referring to? But it would have nothing to do with the microwave. That switch should light up when turned on. Also there would be a pinhole type light next to the switch that tells you when it is trying to light the propane. I'm not sure exactly when that light goes on and off. You have to be smarter than it to figure that out and I am not there yet.
If all else fails and none of us are able to help you I would suggest you call Keystone Customer Service, give them your VIN number, and ask that question. With the age of your unit they may have to check with someone and get back to you.
Good luck. Don't hesitate with any questions on this or any other subject.