BEECH A36 PLT ENCOUNTERS WX DURING VFR ON TOP CRUISE; DIVERTS TO ANOTHER ARPT.

Narrative

I WAS FLYING VFR ABOVE A SOLID OVERCAST ON A FLT FROM ABQ TO CNM. I WAS FLT FOLLOWING WITH ABQ CENTER. I WAS EXPECTING BREAKS IN THE OVERCAST NEAR CARLSBAD; WHERE I COULD DESCENT TO LAND. THE CEILING WAS REPORTED 2500 FT AT THE AIRPORT. UPON REACHING CNM; THE OVERCAST WAS STILL SOLID. I WAS ALSO FLYING THE ACFT'S FD/AUTOPLT SYS. THE CENTER ATC ASKED ME WHY MY INTENTIONS WERE. I SAID I NEEDED AN IFR DESCENT THROUGH THE OVERCAST. AFTER VERIFYING I WAS IFR RATED; HE GAVE ME A CLRNC TO HOLD NE ON CNM VOR AT 8000 FT. I REACHED 8000 FT ON THE AUTOPLT (IN THE CLOUDS); BUT WHEN I TOGGLED OFF THE DESCENT SWITCH; THE AUTOPLT STARTED CLBING AGAIN. I NEVER COULD GET IT TO STABILIZE; SO I DISENGAGED IT AND HAND FLEW THE HOLD; BUT I WAS SO BUSY; THAT I COULDN'T THOROUGHLY STUDY THE ILS 3 APCH AT CNM. (THE RWY 3 ILS WAS THE APCH I SELECTED TO DO. AFTER 4 OR CIRCUITS; I GOT A CLRNC FOR THE APCH; BUT I WAS REALLY BEHIND AT THIS TIME. MY APCH BOOK HAD FALLEN ON THE FLOOR; SO I NEEDED TO FIND CNM ILS 3 AGAIN. TWO OTHER ACFT ARRIVED AND NEEDED THE ILS RWY 3 APCH. I DECIDED AT THIS TIME TO ABORT THE APCH ATTEMPT; AND ASKED FOR A CLB TO VFR AND A HEADING TO ROW WHERE I COULD GET A LOCAL RADAR DESCENT THROUGH THE OVERCAST. I DID THIS WITH A NORMAL LANDING AT ROW -- STRAIGHT FORWARD. LESSONS LEARNED: ALWAYS BE PREPARED. I COULD HAVE STUDIED THE ILS 3 APCH ON THE FLIGHT TO CARLSBAD. UPON ARRIVING; I STILL COULD HAVE CIRCLED ABOVE THE OVERCAST AND STUDIED THE ILS 3 APCH BEFORE ASKING FOR THE IFR CLRNC. DON'T TRUST AUTOPLTS. THE CAN SCREW UP AT THE WORST POSSIBLE TIMES.