A DC9 CREW; DSNDING INTO OMA; OVERSHOT ASSIGNED ALT.

Narrative

CLRED DURING VECTORS TO VISUAL APCH RWY 14R AT OMA TO DSND TO 6000 FT. VMC AND LOOKING FOR TFC ON TCASII THAT HAD NOT BEEN CALLED OUT BY ATC. APCH CHKLIST WAS COMPLETED LATE; AND INCLUDED IN THIS CHK WAS LCL ALT SETTING. I MISHEARD THE SETTING AS 29.60 AND SET THIS. WHEN FO REALIZED THIS; HE POINTED OUT THAT 29.69 WAS CORRECT. AS I RESET TO 29.69 WE WERE APPARENTLY DSNDING THROUGH 7000 FT MSL. MY RESETTING APPARENTLY CAUSED THE ALT ALERT CHIME NOT TO GO OFF 1000 FT PRIOR TO THE 6000 FT MSL SELECTED IN THE WINDOW. FO AND I THEN WENT BACK TO LOOKING FOR TFC THAT WE SHOWED ON TCASII BUT NOT CALLED BY ATC. WE THEN HEARD AN ALT ALERT AS WE DSNDED THROUGH 5700 FT MSL. AS I BEGAN TO MANEUVER BACK TOWARD 6000 FT; ATC SAW DEV AND POINTED OUT THAT WE WERE CLRED TO 6000 FT AND RECLRED US TO 5000 FT. THE REMAINDER OF THE APCH AND LNDG WERE UNEVENTFUL. I CALLED APCH CTL OVER LAND LINE AND APOLOGIZED FOR THE DEV. CONTRIBUTING FACTORS: 1) APCH CHKLIST SHOULD HAVE BEEN COMPLETED SOONER. 2) SHOULD HAVE ENGAGED AUTOPLT WHILE LOOKING FOR TCASII TFC. 3) FO MISSED 1000 FT TO GO REQUIRED CALLOUT. 4) ATC DID NOT ASSIST IN FINDING THE VFR TFC. 5) FATIGUE. CORRECTIVE ACTIONS: 1) BEGIN APCH CHKLIST PASSING FL180 ON DSCNT. 2) QUERY ATC ABOUT UNIDENTED TCASII TARGET AHEAD. 3) MAKE ALL REQUIRED CALLOUTS. 4) ENGAGE AUTOPLT WHILE LOOKING FOR TFC. ADDITIONALLY; BOTH PLTS WERE NEARING THE END OF A LONG CREW DUTY DAY (10 HRS ON DUTY WITH MORE LEGS AHEAD) ON THE 4TH CONSECUTIVE DAY OF FLYING.