A B737-300 CAPT ON APCH TO LAS NOTICED AN UNSAFE GEAR INDICATION; WENT AROUND; DECLARED AN EMER; AND MADE A SAFE RETURN TO LAND.

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ON APCH TO LAS RWY 25L; AT ABOUT 1500 FT AGL L MAIN GEAR LIGHT MOMENTARILY SWITCHED FROM GREEN TO RED AND BACK TO GREEN. DID IT A COUPLE MORE TIMES AND AT 1000 FT WE ELECTED TO GO AROUND AND SEE IF WE COULD FIX THE PROB. WENT THROUGH 'UNSAFE GEAR INDICATION' CHKLIST AND MANUALLY LOWERED THE GEAR. ASKED COMPANY JUMP SEATER RIDING IN THE BACK TO VISUALLY CHK GEAR INDICATION AND GOT BACK IN SEQUENCE TO LAND. AT SHORT FINAL; HADN'T GOTTEN CONFIRMATION FROM JUMP SEATER AND ELECTED TO GO AROUND ONCE MORE. TWR RPTED GEAR APPEARED DOWN. ON THIS GAR; FUEL WAS BECOMING A BIG CONCERN AND I THINK WE HAD ABOUT 3500 LBS. EMER HAD BEEN DECLARED ON FIRST GAR. I BELIEVE IT WAS AT THIS TIME; THAT THE FLT ATTENDANTS CALLED UP TO ASK IF THEY SHOULD 'PREPARE' THE CABIN AND THE FO SAID 'NO;' THINKING; I GUESS; THAT IT'S 99.9% A SENSOR PROB AND THE GEAR IS LOCKED DOWN. JUMP SEATER CALLED UP AND SAID GEAR INDICATION APPEARED LOCKED. TWR CLRED US TO AND ON RWY 25R AND SAID GEAR APPEARED DOWN. LANDED UNEVENTFULLY AND TAXIED TO THE GATE. SEVERAL THINGS I WILL DO DIFFERENTLY: PROBABLY; REQUEST A HOLD; SO WE CAN HAVE TIME TO COMPLETE PROC WITHOUT WORRYING ABOUT GETTING TO RWY BEFORE EVERYTHING IS DONE. IF AN EMER IS DECLARED; THEN POSITIVELY 'HAVE FLT ATTENDANTS PREPARE THE CABIN.' HAVE FO FLY WHILE I TALK TO EVERYONE. I THOUGHT IT WOULD BE BETTER FOR ME TO FLY THIS TIME BECAUSE HE HAD TO DO MANUAL GEAR EXTENSION; BUT IT WOULD HAVE BEEN BETTER 'SITUATIONALLY' FOR ME TO HAVE GIVEN THE ACFT BACK TO HIM AFTER THE GEAR WAS DOWN. I WOULD STILL LAND THE ACFT THOUGH.