Before you dump big $$$$ on a VALVE JOB, consider what Steve Brotherton had to say in this thread:
Average price for a valve job
According to another post that M.B.DOC replied to a long time ago, MB switched to an improved valve guide in April of 1988. Your car is much later than that. It has the improved guides. Alot of 103 motors use a qt. every 1000 miles. If your spark plugs are dry and the car runs good, buy some extra oil and use the money for something else.