I do not think 109K is high at all for a MBenz. I do recall the 140 body having trouble with evaporators, and the repair is expensive, so check to see if it has been done. The repair involves much risk for the mechanic, as a very expensive dash can be ruined during the process if he is not careful. Have a good independent mechanic go through it. This will arm you with information to negotiate the price and perhaps steer you away from the car. Ask the mechanic's opinion, and listen carefully. An experienced mechanic can help you to determine if this is a "good one".
Larry - I am sure you are surprised to find the left hand number in the odometer can be a "1". <bg>
1989 560SEL (172k)
1989 325IC (122K)
2004 Suzuki Volusia LE (3500 miles)
2005 Yamaha Road Star (20 K miles)