Does anyone know the part number for the spark plugs for this car on this site and what else I need to get. It has been 20,000 miles since last tune up. Do I need new wires and caps? How often should I change the transmission fluid.

The plugs and tranny fluid was changed 1 year ago (approx. 18,000 miles ago)

------------------
'89 420 SEL
'90 300 SEL
'84 300 SD (sold it)