ACR CARGO DIVERTING TO DFW AND FLC NOT FAMILIAR WITH ARPT. CLRED RWY 36L AND BRIEFED FOR RWY 36L. LATER REQUESTED TO LAND ON THE RWY 35 COMPLEX AND CLRED TO LAND RWY 35R MAINTAIN 3000 FT UNTIL ON FINAL. IN ERROR TURNED FINAL ON RWY 35C AND CONFLICTED WITH MD80 FOR RWY 35L. CORRECTED TO RWY 35R AND LANDED OK. HAD STARTED A DSCNT ON RWY 35C AND GOT TO 2700 FT CAUSING THE CONFLICT.

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WHILE APCHING DFW FROM THE NW; WE BROKE OUT OF AN OVCST AND FLEW A L DOWNWIND TO DFW. WE WERE ASSIGNED RWY 36L AND BRIEFED FOR A VISUAL APCH BACKED UP BY THE ILS. AS WE NEARED THE ARPT WE DECIDED TO ASK FOR A RWY ON THE E SIDE TO REDUCE TAXI TIME TO THE NE CARGO AREA. APCH THEN ASSIGNED US RWY 35R. WE WERE VECTORED OVER THE FINALS FOR RWY 36L/R AND RWY 35L AT 3000 FT MSL. WE WERE HANDED OFF TO TWR AND ADVISED TO MAINTAIN 3000 FT MSL UNTIL TURNING FINAL FOR RWY 35R. AN MD80 WAS ON FINAL FOR RWY 35L AND ADVISED US 'IN SIGHT' TO TWR. I WAS LOOKING FOR AN ILS FREQ FOR RWY 35R AS THE PF TURNED TOWARD THE ARPT. RWY 35R HAS NO INST APCH. THE FO STARTED TO DSND AS WE WERE HIGH AND IN CLOSE TO THE ARPT. WE THEN REALIZED WE WERE ACTUALLY LINED UP ON RWY 35C. THE RWYS WERE RECENTLY RENUMBERED AS THE NEW RWY 35R WAS OPENED -- AS WE TURNED BACK TO THE E AND RWY 35R. TWR SCOLDED US FOR LINING UP ON RWY 35C AND DSNDING TO 2700 FT MSL. THE LAST MIN REQUEST FOR AN E RWY NEGATED OUR APCH BRIEFING. WE SHOULD HAVE STAYED WITH OUR ORIGINAL RWY OR FLOWN A WIDER PATTERN TO THE NEWLY ASSIGNED RWY. AT THE VERY LEAST WE SHOULD HAVE STUDIED THE ARPT DIAGRAM SOONER; WE HAD BEEN DISPATCHED TO DFW INSTEAD OF OUR NORMAL DEST BECAUSE OF WX. FATIGUE WAS A SMALL FACTOR HERE; BUT BASICALLY WE ALLOWED OURSELVES TO BE RUSHED INTO A VISUAL APCH TO A BUSY UNFAMILIAR ARPT.