'91 350sd valve adjustment
 

How often should the valves on this 603 engine be adjusted? I bought her at 106k and now have 115k. I didn't receive any records or manuals and the owners manual I ordered from MB is elementry, i,e. how to turn on your lights, tire pressure etc. There is also a switch in the back of the glove box and I don't know it's purpose. Can anyone enlighten me to its function?:)

These values do not need regular adjustments like that ones in OM61x.