AFTER A RWY CHANGE WAS ANNOUNCED FOR SFO; AN INBOUND B767 CREW BECAME BUSY RESETTING NAV EQUIP AND STARTED DSCNT TO THE WRONG ALT.

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ATC FACILITY: ZOA. LOCATION: MOD 245 DEG RADIAL; APPROX 16 DME. THE ALTDEV OCCURRED AFTER MODESTO INTXN; WHILE ON APCH AND DSCNT TO CEDES INTXN. BOTH THE FO AND I WERE TASK SATURATED WITH SWITCHING FROM THE LOCKE 1 ARR AND LNDG ON RWY 19L; TO THE MODESTO 2 ARR AND LNDG ON RWY 28R; PLUS A DSCNT AND BEING GIVEN A HOLDING PATTERN AT CEDES INTXN AFTER PASSING MODESTO. I ABSOLUTELY BELIEVE I HAD HEARD A DSCNT CLRNC TO 11000 FT FOR HOLDING AT CEDES. I AM NOW SURE THAT WAS A RESULT OF ME STARING AT THE MODESTO 2 ARR (WHICH SAYS TO EXPECT CLRNC TO CROSS AT 11000 FT; 250 KTS) AT THE SAME TIME ATC ISSUED THE DSCNT/HOLDING CLRNC. I WAS REPROGRAMMING THE FMC AS THE FO RESET THE MCP TO 17000 FT -- DID NOT CATCH IT. AS THE ACFT WENT INTO ALT CAPTURE AT 17000 FT; I LOOKED OVER AND SAW THE 17000 FT IN THE WINDOW AND THOUGHT IT HAD BEEN INCORRECTLY SET. I SAID 'NO; THEY WANT US TO CROSS CEDES AT 11000 FT. RESET THE MCP TO 11000 FT.' THE FO WAS BUSY SWITCHING PLATES TO THE NEW ARR AND RWY; AND DID NOT HEAR ME OR NOTICE MY ACTION. AT APPROX 15000 FT; ATC ASKED US TO VERIFY OUR ALT. I REPLIED; 'WE ARE OUT OF 14000 FT; DSNDING TO 11000 FT.' ATC SAID TO TURN R TO 310 DEGS AND CLB TO 15000 FT. AFTER ACCOMPLISHING THAT; WE WERE TURNED BACK TO CEDES; DID 1 TURN; AND WENT ON IN AND LANDED. THERE WERE NO TCASII ALERTS. I FEEL MY BIGGEST MISTAKE WAS NOT THE 11000 FT ERROR; BUT RATHER NOT QUESTIONING THE FO AS TO THE ALT HE HAD SET.