If it threaded back in you might be ok.  Won't hurt anything to try it.  I've only ever seen them wipe the threads out completely or unscrew and leave them intact.  $200 to put an insert in #7 sounds like a deal--3,4,7 and 8 are a PITA to get to.  FWIW I had one unthread in my CVPI and it threaded right back in a few thousand ago and has been good.  You can hear them when they get loose before they spit, sounds just like an exhaust leak.