A CL600 FLIGHT CREW RECEIVED A LANDING GEAR WARNING ON APPROACH. THEY EXECUTED A GO-AROUND; RAN THE PROCEDURE AND LOWERED THE GEAR MANUALLY. THE FIRST OFFICER EXPRESSED HIS CONCERN THAT THE PROBLEM MAY HAVE BEEN RELATED TO MAINTENANCE ACTION SINCE THE AIRCRAFT WAS JUST RELEASED FROM A SERVICE CHECK.

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ON APCH TO ZZZ AFTER RECEIVING A VISUAL CLRNC FROM ZZZ APCH; I WAS SLOWING THE ACFT TO APCH SPD. I CALLED FOR FLAPS 8 DEGS AT 210 KIAS; THEN FLAPS 20 DEGS AT 200 KIAS; ZZZ APCH THEN HANDED US OFF TO TWR. AS I WAS SLOWING THROUGH 180 KIAS; I CALLED FOR 'GEAR DOWN; FLAPS 30 DEGS.' AS THE GEAR HANDLE WAS LOWERED TO THE DOWN POS; A MASTER CAUTION APPEARED FOR 'HYD 3 LOW PRESSURE;' THEN AROUND 1 SECOND LATER THE MASTER WARNING FOR 'GEAR DISAGREEMENT' ALONG WITH AN AURAL ANNUNCIATOR STATING THE 'GEAR DISAGREEMENT' VERY LOUDLY. THE CAPT AND MYSELF WERE A LITTLE STUNNED AS THIS WAS OUT OF THE ORDINARY AND AT A LOW ALT. WE WERE FOCUSED ON THE LNDG AND NOT READY FOR A MALFUNCTION. I SAID 'CANCEL AND IDENT' WHICH IS THE STANDARD CALLOUT; AND RIGHT AS I SAID THIS; ZZZ TWR SAID 'ACFT X CLRED TO LAND RWY XL.' THE CAPT COULD HARDLY HEAR THIS AND I TOLD HIM TO TELL TWR THAT WE WERE GOING AROUND. HE SAID 'WHAT? IT IS SO LOUD; I CAN'T HEAR YOU.' I DO BELIEVE THAT HAD THE AURAL ANNUNCIATOR ONLY SAID 'GEAR DISAGREEMENT' ONCE IT STILL WOULD HAVE GOTTEN OUR ATTN WITHOUT BEING A DISTR. AFTER INITIATING THE GAR BY CALLING FOR 'FLAPS 8 DEGS; TOGA THRUST;' I CALLED FOR AUTOPLT ON; WHICH WAS OUT OF SEQUENCE. I REALIZED THIS WHEN THE AUTOPLT PITCHED UP TOWARDS THE GAR FLT DIRECTOR COMMAND BARS. MEANWHILE; TWR HAD GIVEN US A HDG AND PUT US BACK ON WITH ZZZ WHO GAVE US 3000 FT AND A HDG TOWARDS THE S. AFTER STABILIZING THE ACFT BY HAND; I THEN CALLED FOR AUTOPLT ON AND WE STARTED TO RESOLVE THE SITUATION. THE CAPT RAN THE CHKLIST AND I HANDLED THE RADIOS. THE SITUATION WAS RESOLVED WHEN THE GEAR WAS BROUGHT DOWN BY USING THE EMER MANUAL GEAR EXTENSION. I THEN NOTIFIED TWR THAT OUR NOSEWHEEL STEERING WOULD BE INOP ON LNDG. I THEN HANDED THE CTLS OVER TO THE CAPT FOR THE UNEVENTFUL LNDG. AFTER LNDG; THE NOSEWHEEL STEERING WAS NOT WORKING; SO THE CAPT TURNED THE ACFT OFF THE RWY USING DIFFERENTIAL PWR AND WE STOPPED ON THE TXWY; CALLED FOR A TOW IN TO THE RAMP AND LET GND KNEW THAT THE EMER WAS OVER. I BELIEVE THAT THIS WAS CAUSED BY A LACK OF PROPER MAINT SUPERVISION OR A LACK OF PROPER KNOWLEDGE OR PROCS BY MAINT PERSONNEL. THE COMPANY IS IN FINANCIAL DIFFICULTY RIGHT NOW AND I COULD IMAGINE THAT THEY WOULD CUT SHORT THE COST OF PROPER MAINT. I SAY THIS BECAUSE THE AIRPLANE WAS JUST RETURNED TO SVC FROM A #1 ENG SWAP AND SVC CHK JUST YESTERDAY.