B727 FLC CLBS ABOVE ASSIGNED ALT. ALT HOLD FAILED TO CAPTURE; CAPT WORKING ON SETTING A WAYPOINT IN GPS.

Narrative

COMPANY'S RELATIVELY NEW PAX OPS; WITH NEW GPS ONBOARD ON A NEW RTE. FO WAS FLYING; CAPT WAS DETERMINING HOW TO ENTER WAYPOINT IN GPS. FE WAS CALCULATING CRUISE EPR FOR ALT FL310. 1000 FT ALERT AND STANDARD '1000 FT TO GO' CALL MADE. AT ABOUT 150 FT PRIOR TO ALT FO ARMED ALT HOLD; HOWEVER; AUTOPLT NEVER CAPTURED. SECONDS LATER WE GOT 250 FT OFF ALT WARNING; FO DISARMED AUTOPLT; LEVELED OFF AT 31400 FT AND BEGAN IMMEDIATE DSCNT TO 31000 FT. ATC QUERIED OUR ALT; INFORMED US WE SHOWED 400 FT HIGH. I FELT THAT AT A BUSY TIME IN THE COCKPIT WITH SOME UNFAMILIAR EQUIP ON AN UNFAMILIAR RTE WE SHOULD HAVE BEEN MORE VIGILANT. I SAW THE FO ARM ALT SELECTOR AND THEN RETURNED TO CALCULATING CRUISE DATA INSTEAD OF WATCHING AUTOPLT LEVELOFF THE ACFT. FO WASN'T MONITORING AUTOPLT AS CLOSELY AS HE SHOULD HAVE. CAPT NEEDS TO FAMILIARIZE HIMSELF MORE CLOSELY WITH DIFFERENT FUNCTIONS OF GPS. OVERALL I FELT FAMILIARITY WITH ACFT AND ITS OPS IN CARGO LED TO A FALSELY PERCEIVED COMFORT ZONE WITH PAX OPS WHICH HAS DIFFERENT EQUIP ONBOARD; TAKES US DIFFERENT FLT PLAN RTES. THIS MISCONCEPTION LED TO RELAXED CREW VIGILANCE. HENCE AN ALT INCURSION.