Wires from meter to disconnect to junction to home
It sounds like your service starts at 100A at the meter, then runs to a 50A box, then into your 100A panel (possibly since this is a park, the 100A meter runs 2x 50A boxes - yours and your neighbors?). It also sounds like there are some concerns about how the 50A box is (not) grounded. If I understand correctly, the park owner is promising to make repairs and you are concerned about making sure that the correct work is done properly.
As long as the 50A box is just tied in to the circuit (not protecting your home), your main concern would be making sure that if and when there is a device plugged into the 50A receptacle box, your home + that device is not drawing more than 100A
I'm not an electrician, but it sounds to me that if you make sure that you have a proper ground you will be fine.