I just purchased a 1988 300E and have a lot of questions and some problems with the vehicle I hope someone can help me with.


Power steering:

What kind of fluid should I use and how full should I fill the reservoir, I have not found any full markings? How much fluid should I buy if I am going to replace the filter?


Is the motor a M103 and how do I find the body style?


Fuel Filter:

When trying to purchase a fuel filter I see the following message:
Optional 002 477 13 01 can still be used on early models with single fuel pump. New filter 002 477 44 01 is designed for tandem pumps where greater volume and dampening effect is needed.
OR
Optional with 002 477 17 01
Which fuel filter do I need?


Problems:

Rear interior light will not come on at all including when doors are open with switch on dash in both positions.
(Bulb test good no voltage at bulb, rear door switch good ground present at door switch)

Front interior light only comes on by the switch or the passenger front door.
(Drivers door switches both test good ground applied to one and 12V to the bottom one, I assume the top one (ground) works the light what does the bottom (12V) switch work?)

Front drivers door will not lock other doors but sets alarm. Passenger door locks all doors.

Does 1988 300E have a cabin air filter?