AN ACR ACFT APCHING DFW FAILED TO SELECT A NEW FMS RWY FOLLOWING A RWY CHANGE AND DEVIATED INTO ANOTHER RWY'S FINAL WITHOUT CAPTURING THE PROPER LOC.

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WE WERE FORCED TO DEVIATE ABOUT 30 MI W AROUND WX AS WE CLBED OUT OF ZZZ. WX IN DFW WAS 900 FT OVCST. AS WE APCHED DFW; ATC CHANGED OUR ARR TO ONE THAT FAVORED THE W SIDE RWYS. WE DISCUSSED THE PROBABILITY OF A PLANNED RWY CHANGE; AND ELECTED TO BE READY FOR IT. ON OUR DSCNT; HOWEVER; ATC MENTIONED THAT THEY WERE TRYING TO COORDINATE WHICH RWY TO GIVE US; AND WE TOOK THAT AS AN ATTEMPT BY THEM TO GIVE US OUR ORIGINAL E SIDE RWY IF THEY COULD. WE THEREFORE DELAYED SETTING UP AND RE-BRIEFING THE APCH. ATC EVENTUALLY DECIDED JUST TO KEEP US ON THE W SIDE; AND WE BRIEFED THE APCH AS WE DSNDED FROM 11000 TO 6000 FT ON DOWNWIND. WHAT WE FAILED TO DO IN OUR RUSH TO COMPLETE EVERYTHING; WAS RE-ENTER THE APCH IN OUR FMC. AS WE WERE GIVEN A TURN TO BASE WE WERE SLOWED TO 170 KTS AND CONFIGURED ACCORDINGLY. RIGHT AFTER WE WERE CLRED TO INTERCEPT THE LOC; THE FO WAS DISTR BY A STUCK MIKE ON THE FREQ; AND WAS TRYING TO GET A WORD IN OR FIND ANOTHER USABLE FREQ. THE ACFT CAPTURED THE LOC JUST LIKE IT WAS SET UP TO DO; BUT BECAUSE THE FMC WAS STILL SET UP FOR A PARALLEL APCH ON THE E SIDE; I PERCEIVED IT AS AN EARLY CAPTURE; AND SELECTED A HDG UNTIL I COULD SORT THINGS OUT. I WAS HAND FLYING IN IMC CONDITIONS; WITH MY FO HEAD-DOWN DISTR AND LOOKING FOR A WORKING RADIO FREQ. I MANAGED TO WANDER FAR ENOUGH E OF THE LOC TO GET EVERYONE'S ATTN; AND THE FIRST UNGARBLED RADIO XMISSION WE RECEIVED WAS AN ATC HDG CHANGE TO GET BACK ON COURSE. WE COMPLETED THE APCH AND LNDG SAFELY; BUT IT WAS A VERY LONG AND EMBARRASSED TAXI TO OUR GATE ON THE OTHER SIDE OF THE ARPT. SUPPLEMENTAL INFO FROM ACN 763455: WE WERE LATER ASSIGNED RWY X AND THE CAPT REVIEWED THE BRIEF. WE DID NOT VERIFY WHAT WAS IN THE BOX. VECTORED FOR A LONG APCH DUE TO TFC WE FINALLY WERE TURNED BACK TO FINAL AND WERE INSTRUCTED TO INTERCEPT THE RWY X LOC AND CONTACT TWR. WE HAD ALREADY TUNED AND IDENTED THE RWY X LOC CORRECTLY. AS WE TURNED TO INTERCEPT I DID NOT NOTICE THE DISCREPANCY BTWN THE LOC AND THE MAP (WHICH SHOWED RWY Y). WE WERE IMC. I SWITCHED TWR AND ENCOUNTERED STEADY SIDE TONE AND UNUSUAL INTERMITTENT TONES. I DOUBLE CHKED THE FREQ AND CONTINUED TO RECEIVE SIDE TONE; AS IF THERE WAS A STUCK MIKE ON THE FREQ. I TRIED TO CALL TWR 2 TO 3 TIMES AND GOT NO RESPONSE. I BECAME TOO INVOLVED WITH THE COM PROB AND THEN NOTED THE DISCREPANCY BTWN THE LOC AND THE MAP. I SAID 'SOMETHING IS NOT RIGHT.' AT THAT SAME TIME THE CAPT HAD BEGUN A TURN BACK TO THE L AND WE HEARD A CALL FOR XXX TO TURN IMMEDIATELY TO INTERCEPT THE RWY X LOC. THIS CALL MAY HAVE BEEN ON GUARD; WHICH WE WERE MONITORING. WE CONTINUED THE TURN AND I RESPONDED ON TWR WITH OUR POS. AFTER MY RESPONSE COM WE HAD GOOD COM WITH TWR. WE HAD FLOWN OVER NEAR THE EXTENDED CTRLINE OF RWY Y WHILE COM WITH TWR WAS SEVERELY DEGRADED/IMPOSSIBLE. THE REST OF THE APCH AND LNDG WAS ROUTINE AND UNEVENTFUL. THE CHAIN OF EVENTS FOR ME IN THIS INCIDENT IS: PREMATURE SELECTION OF LNDG RWY IN FMS; CHANGE OF ARR PROC; INCOMPLETE APCH BRIEF; POOR FO XCHK; IMC; COM FAILURE ON TWR FREQ.