FLC OF AN MLG OVERSHOT FINAL DURING A VISUAL APCH RESULTING IN LTSS WITH ANOTHER ACFT ON APCH TO A PARALLEL RWY.

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IT WAS A CLR DAY; ARR INTO MCO. WE HAD PREVIOUSLY LOST QUANTITY IN R HYD SYS DURING CRUISE FROM EWR TO MCO. CAPT WAS FLYING AIRPLANE. WE STILL HAD ENOUGH HYDS TO CONFIGURE AND BRIEFED WE WOULD DROP GEAR AND FLAPS EARLY. WITH AUTOPLT ENGAGED WE WERE CLRED TO INTERCEPT THE RWY 17 LOC FROM THE NE. I WAS RUNNING THE CHKLIST AND CONFIGURING THE ACFT BUT I DID NOTICE THAT THE CAPT HAD ARMED THE ILS FOR THE INTERCEPT. JUST OUTSIDE THE RWY 17 MIDDLE MARKER; APCH TOLD US TO TURN BACK L TO INTERCEPT (WE OVERSHOT FINAL) AND IF WE HAD A SMALL TWIN IN SIGHT THAT WAS ON THE RWY 18L APCH. THE CAPT (WHO WAS WATCHING ME CONFIGURE THE ACFT) IMMEDIATELY DISCONNECTED THE AUTOPLT AND TURNED L TO INTERCEPT RWY 17. I LOOKED OUT AND SAW THE TWIN ON RWY 18L. THERE SEEMED TO ME TO BE AMPLE SEPARATION. WE NEVER RECEIVED A TA OR ANY OTHER TCASII WARNING. THE APCH WAS CONTINUED AND COMPLETED WITHOUT FURTHER INCIDENT. THE CAPT CALLED APCH CTL AND WAS TOLD WE GOT WITHIN 1/2 MI OF THE TWIN (100 FT VERT). THE HYD PROB WAS A CONTRIBUTING FACTOR (TAKING THE CAPT'S ATTN AWAY FROM THE APCH) BUT THE AUTOPLT SHOULD HAVE INTERCEPTED THE COURSE; FOR IT WAS ARMED. THE OVERSHOOT WAS NOT THAT GREAT AND I HAD THE TWIN IN SIGHT THE WHOLE TIME. APCH CTL DID SAY THAT AS FAR AS THEY WERE CONCERNED THE MATTER WAS CLOSED; AND THERE WOULD BE NO FURTHER ACTION.