Also, wagons have SLS suspension on the back, be sure to drive it and make sure the backend isn't saggy and swoony or expensive repairs will be needed. The M112 engine is prone to leaking valve covers, leaking "window" gasket on the front of the engine below the oil filter, and EGR tubes that carbon up - all are easy to address. You should listen to the catalytic converters, they are common replacement items at the age of your car and about $800 per side for plug-and-play. The socket on the transmission tends to leak trans fluid (an easy replacement), but neglect will lead to fluid wicking up the wiring and ruining the transmission control module. Lower ball joints on the front suspension should be checked - they are common wear items. Overall, look for records and signs of problems being taken care of along the way. A neglected W210 easily needs $3000-$4000 in the average shop to get problems fixed that were due to neglected maintenance.