1989 300E Air Filter Replacement

[think300E]

What brand of Air Filter do you use?

I see peachparts appears to have the lowest price for air filters (as opposed to local auto parts and amazon).

The picture between the shops do not match up against each other (and since it has been replaced by the mechanic I do not know what it looks like - certainly would remove before ordering).

I am mainly interested in the brand of Air Filter and any potential gotchas in terms of replacing it. Does the brand matter (better quality?)
Any other parts I need to replace?

How to tell if it needs to be replaced? I guess if its very dusty that is the sign? can it be washed?

http://www.allpartsexpress.com/ShopByVehicle.epc?q=1989-MERCEDES--BENZ-300e--/l6_3.0l-Filters&yearid=1989%40%401989&makeid=MERCEDES+BENZ%40%40MERCEDES+BENZ&engineid=1193846%40%40300E+%2FL6%5F3%2E0L&catid=Filters&subcatid=Air Filter&mode=PA

http://catalog.peachparts.com/ShopByVehicle.epc?q=1989-Mercedes--Benz-300e-Air--Intake&yearid=1989%40%401989&makeid=63%40%40MERCEDES+BENZ&modelid=6201%3AED%7C10000013%3AMBC%7C1507%40%40300E&catid=240497%40%40Air+Intake&subcatid=240499@@Air+Filter&mode=PD

Thanks