HI, i own a 98 E320 also, i've hooked up a factory 6 disc cd changer to the 10 pin connector inside the truck. i believe the changer is an alpine unit made in china. it costs 700 us if you buy it from the dealers. as far as the head units are concerned, i've seen posts here describing the installation of aftermarket units on c280s and c320s.

not sure if this helps, but good luck!

theo