What's the serial number? Cross check here...
http://glocktalk.com/forums/showthread.php?t=268364
Yes, it's fine to shoot +P, says so in the manual and on the Kahr web site.
Generally tritium lasts about 10 years. Kahr sights are small to start with. I believe the youngest your pistol could be is six years old (2003), but could be 11 years old now.