The best piece of advice you have been given is to go to winnebagoind.com, go to the resources tab and find the schematics for your rig. The electrical schematics are a little confusing at first but they give the general location of almost everything electrical.
After see your pictures and the fact that you keep asking for a ground wire location leads me to believe you are not very knowledgeable about wiring practices in motor vehicles.
So to start, do you have a meter or a 12vdc test light? If you do not, your going to need one or the other.
Trouble shooting a lack of power to a system usually starts at the beginning. Find the fuse and check to see if there is power to that point, if there is power on both sides of the fuse, the next point is determine if there is any pint at which the wire from the fuse goes to a junction point before you get to ON/OFF switch on the control panel. You will need each junction point until you get to the switch. If there is power to the panel and it goes through the ON/OFF switch, I think you are going to need a tech guy to help you.
Usually, there is no ground WIRE per say. Most devices use the chassis ground. Judging from the photos you provided, you could well have problems in your battery box. I think that there is a lot of possible damage to the system judging from the lack of maintenance on the HWH system. It needs cleaning.
Good luck and let us know what happens.
