AEROSTAR 601P ACFT ON ARR AND APCH IN IMC; RPTR PLT BECAME DISORIENTED AND DIDN'T HAVE THE PROPER APCH CHART FOR THE ASSIGNED RWY. APCH CTLRS HELPED RPTR WITH VECTORS; FREQS; ETC. INITIALLY; AN AUTOPLT MALFUNCTION CONTRIBUTED TO RPTR'S DIFFICULTY.

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I WAS ON AN IFR FLT FROM APA TO SLC IN IMC. ON MY INITIAL CLRNC; I WAS GIVEN EXPECT MYTON; SPANE 3 ARR. SOMETIME PRIOR TO ARRIVING AT MYTON; I LOST MY AUTOPLT. IT WENT INTO A STEEP CLB AND AN AUDIBLE BUZZER WENT OFF. THE ONLY WAY I COULD SHUT IT DOWN WAS BY SHUTTING DOWN THE AUTOPLT MASTER SWITCH. AT MYTON I WAS GIVEN A DSCNT TO 15000 FT AND DIRECT TO FAIRFIELD. I WAS TUNING IN TO ATIS FOR SLC AND LOOKING AT THE SPANE 3 ARR. LOOKING AT SPANE 3 I WAS EXPECTING A RWY 16 APCH. APCH ASKED MY SPD AND I RESPONDED 220 KTS. HE ASKED ME TO SLOW TO AND HOLD 190 KTS AND DSND TO 11000 FT. I FINALLY CAME AROUND THE POINT AND GOT ATIS. IT SAID LNDG RWY 34R AND RWY 35. THE CTLR THEN SAID EXPECT LOC RWY 34R ALTHOUGH FOR SOME REASON I MISUNDERSTOOD AND WROTE DOWN RWY 35R ON MY KNEE BOARD. I THEN FRANTICALLY LOOKED IN COMMERCIAL CHART FOR A LOC RWY 35R TO NO AVAIL. BOTH MY PAX AND MYSELF LOOKED. WHILE LOOKING; I WAS TOLD I HAD GONE THROUGH THE OM. THE CTLR WAS VERY PATIENT WITH ME AND GAVE ME THE CORRECT FREQ FOR RWY 34R AFTER I HAD TUNED IN RWY 34L IN MY PANIC STATE. ALL THE WHILE IN ADDITION TO MY CONFUSION I HAD HELD 70% PWR TO MAINTAIN 190 KTS. WITH THE CTLR'S HELP I DID LAND ON RWY 35 AFTER EXECUTING A RWY 34R APCH. I WAS NOT PREPARED FOR THE APCH AND WHEN THE AUTOPLT WENT OUT IT MADE IT MORE DIFFICULT TO PREPARE MYSELF. IN ADDITION; I TRIED TO MAINTAIN 190 KTS WHICH IS AT LEAST 50 KTS FASTER THAN I SHOULD HAVE ALLOWED. THE CTLRS WERE VERY GOOD TO WORK WITH AND SAVED THE DAY FOR MY MISTAKES.