You should replace the bulbs that are not operating correctly. You also should go ahead and replace all of the bulbs that are black in color. (Use only the correct wattage bulbs found at German supply houses. Don't use the american equiv.)
The SRS should be checked out by a tech. Most of the time the slip rings are faulty and have to be replaced.
The ODO is electronic on your car and will have to be checked. Most of the time, I have replaced the speedo heads for this problem.
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS