Can civilians who buy ex-military fighter jets get the necessary maintenance information for them?
Most military surplus aircraft are considered by the FAA to be experimental exhibition aircraft and subject to the rules and maintenance requirements for experimental aircraft.  That being said, most owners seek out retired military personnel who did maintenance on these aircraft and currently work as AIs (authorized inspectors) in civilian aviation to handle maintenance and repairs.  Firms like Code 1 Aviation and Thornton Aircraft specialize in certain types of military aircraft and have collected libraries of maintenance manuals and other resources for owners and can perform maintenance conforming to the old military and civilian experimental aircraft guidelines.