I agree with Brian that a good one at the miles you said can fetch around $5K. This one with just over 200K miles went for $4500.
http://cgi.ebay.com/ebaymotors/Mercedes-Benz-300-Series-300D-MERCEDES-300D-TURBO-DIESEL-W123-300TD-CD-SD-CLN-CA-CAR_W0QQcmdZViewItemQQcategoryZ6330QQitemZ4605954447QQrdZ1QQsspagenameZWDVW