You'll probably have better luck finding someone with a working deck than resuscitating one yourself. First place I would start is this website:
http://www.angelfire.com/alt/cartrivision/
Check with the guy who put the site up; he appears to have one or access to one (You might not have found it if you were googling "Cartravision" rather than "Cartrivision.")
There are also commercial vendors who specialize in obsolete videotape playback and restoration; you'll spend some money but given the situation and the value of your material, it would probably be well spent. Best of luck with it.