2008 ml 350 wipers don't work, rear deck won't open, turn indicators don't work, interior lights don't come on when door is opened, gas gauge doesn't work

SOURCE: Auto electrical problems with 02 MB E320

Hi, you will have to get your car pluged into a Diagnostic computer with MB software.
It may just be a case of reseting the system.
But if it comes to the worst one of the SAM (can system) units has gone a little faulty & can only be replaced & reprogramed using MB computer system at a Merc garage or a top Diagnostic garage.

SOURCE: Passenger Side Rear Door Will Not Open

If you can lower the window down you can jimmy it open from there preferably from the inside has more padding in the inside seal compared to the outside one i can see the switches working but some how it detached itself try and hook around the area were the door latch is not door hinges lol it wont be an easy task but a thin coat hanger as well as possibly a rubber door stopper to give ya some space to work with may help out good luck take her easy with the door stopper don't push it in too far may crack the plastic 

SOURCE: re-setting service indicator on ml 320 2008

This Can Be DONE BY Disconnecting Battery For 5-10 Mins.

SOURCE: intermittent wiper, turn indicator, rear screen demister not work

Electrical problems are rife in these models. Try replacing the relevant relay box - a black box situated in the fuse box bay. This will hopefully solve your problem. Good luck!

SOURCE: What I need to do

SERVICE B REPLACE CLEANER FILTER, INSPECT SERVICE BRAKE SYSTEM, REPLACE CABIN AIR FILTER, LUBRICATE DOOR HINGES AND LATCHES,REPLACE ENGINE OIL AND FILTER,INSPECT SERVICE EXTERIOR LAMPS, READ CLEAR FAULT CODES, TOP OFF FLUID LEVELS,LUBRICATE HOOD LOCKS, INSPECT SERVICE INTERIOR SWITCHES,INSPECT ADJUST PARKING BRAKE,RESET SERVICE INDICATOR LIGHT,INSPECT SERVICE STEERING AND SUSPENSION, LUBRICATE SUNROOF GLIDES,INSPECT ADJUST TIRES AIR PRESSURE,ADJUST LUBRICATE THROTTLE LINKAGE,REPLACE WINDSHIELD WIPERS.NOW 60000 MILES INTERVALS YOU NEED FLUSH BRAKE FLUID,FLUSH COOLANT,REPLACE FUEL FILTER,REPLACE POWER STEERING FLUID,REPLACE SPARK PLUGS,REPLACE TRANSMISSION FLUID AND FILTER.