the light you described seems to be the low coolant light. Could be a loose connection or sensor.

If you call 1-800-for-mercedes
you can order a new car owners manual plus order a booklet of approved lubricants

Check out Haynes for a manual, www.haynes.co.uk

Ebay may even have actual MB service manuals.

You may want to join The Mercedes Benz Club -www.mbca.org-
has a diesel technical advisor that is an incredible source of info on the 190's, he owns multiple 190's

also consider joining the following club by applying to email to, club-request@mbz.org with SUBSCRIBE as text ~~ it is an e-mail list dedicated to all things Mercedes