Thy're very low hours. I've never heard of heads wearing out in a DV device. Bearings do. Have a listen to it in operation. If it sounds OK it probably is. Check the zoom motor for mechanical noise. Check the bottom where the tripod mounting is for cracks. Check that the firewire and composite output RCA connectors work and aren't loose.
About all I can think of. Don't pay too much!

Bob.