I had the valve stem seals replaced on my '88 560SL and it cost about $700. I think it's about $50 in parts and a whole bunch of labor. I was using about a quart of oil for every 100-150 miles.
The bulb is a little 2W bulb with a micro-compression? fitting. I couldn't find one at an auto parts store, but a bulb specialty shop had tons of them. They cost about $1. I know Sylvania makes the right size.
1988 560SL Black/Palomino
1988 300SEL Black Pearl/Burgandy
1984 500SEC Anthracite Grey/Palomino