I know, I f'd up, I replaced me G500 battery and reversed the terminals... Now I have major issues, I checked and replaced all the fuses & relays with no change. I want to take it to the dealership but the transmission wont come out of low mode and none of the lights work. What else can I check to get the transmission and lights to work. Desperate!

 

There's a main fuse that may have blown and will need to be replaced.

If the car won't come out of park then you'll have to tow it to the dealer. There's no way to get the car into neutral except electronically.

Call Mercedes roadside and make sure they get a towing company who has dollies. Flat beds and winches will do no good.

 

If the car's electrical system is completely dead, it could be the main fuse of one (or more) of several main fuses. You should find these mounted near the battery positive (red) cable. Disconnect the battery's negative terminal, wrap it in a towel and secure it away from the battery. Then get a digital voltmeter and using the resistance (ohms) setting, check the continuity across the fuse(s) terminals; resistance should measure close to zero ohms. If a blown main fuse(s) is all that happened, you will be indeed a very lucky fellow. If you replace one or more of these, and they immediately blow, you are not so lucky -- call the tow truck.