The Autohelm 6000 is supposed to be a good unit. While Raytheon (the former parent company of Autohelm) has sold off its consumer marine division, Raymarine has purchased what used to be Autohelm and is still servicing and producing the 6000. Raymarine has a website that is quite helpful. Raymarine supposedly has a good service department for their equipment and do a good job of repairing and rebuilding many of their products. I would start with Raymarine. West Marine sells Raymarine products and you might also try them for replacement parts.
Jeff