I think your price is just about right, got this from Kelly's Blue Book:
2000 Mercedes-Benz ML-Class ML320 Sport Utility 4D
Engine: V6 3.2 Liter
Trans: Automatic
Drive: 4 Wheel Drive
Mileage: 71,000
Equipment:
Air Conditioning, Power Steering, Power Windows, Power Door Locks, Tilt Wheel, Cruise Control, AM/FM Stereo, Cassette, Multi Compact Disc, Premium Sound, Navigation System, Dual Front Air Bags, Traction Control, Leather, Dual Power Seats, Skyview Roof, Roof Rack, Privacy Glass, Running Boards, Grille Guard, Premium Wheels
Retail Value: $23,040
The Kelley Blue Book Suggested Retail Value is representative of dealers' asking prices and is the starting point for negotiation between a consumer and a dealer.
Hope this helps, and good luck