any suggestions on sight replacement on this model auto ? nice weapon but is it worth it any thoughts on it?

To my knowledge there were never any factory Tritium night sights for the 469 or 669.  The front sight had a red vertical line on the 669 and yellow vertical line on the 469 with a rounded white outline rear sight.   The 6904/6906 could be purchased with Novak Tritium Night Sights.  



Years ago Trijicon would drill out front sights on guns with fixed front sights and add a Tritium ampoule.   The best solution today would have someone mill off the front sight and mill in a dove tail for new front sights.   Unless you’re a machinist not really practical on an old 669 since S&W no longer supports that model.