PLT OF A C182 OVERSHOT ASSIGNED ALT DURING CLBOUT RESULTING IN CTLR INTERVENTION AND THE RPTR RETURNING TO ASSIGNED.

Narrative

PROB AROSE WHEN CTLR DISCONTINUED VECTORS AND TOLD ME DIRECT MY DEST; WHICH WAS ONLY ABOUT 20 NM FROM DEP ARPT (HAYWARD DIRECT CONCORD). I WAS CONFUSED BY 'DIRECT TO CONCORD;' WHETHER VOR OR ARPT. CTLRS WERE VERY BUSY AND I DIDN'T CLARIFY. IN TRYING TO ORIENT MYSELF (UNFAMILIAR AREA; AIRSPACE); I LET THE PLANE CLB THROUGH ASSIGNED ALT (5000 FT MSL) TO 5500 FT MSL. CTLR ALERTED ME AND I RETURNED TO ALT. THE INTENSITY OF THE RADIO TFC MADE COM DIFFICULT. MY CONFUSION WAS AGGRAVATED BY A CIRCLING CLB TO 5000 FT AND THEN A RELEASE 'DIRECT TO....' I LATER DETERMINED THAT THE CTLR HAD POINTED ME AT THE VOR FOR THE NORMAL LDA APCH TO CONCORD. BECAUSE THE DISTANCE WAS SO SHORT; I FOUND MYSELF CONTINUOUSLY BEHIND ON THE NAV. TO AVOID FURTHER DEVS; I CANCELED OVER THE DEST AND COMPLETED THE FLT VFR (AT THE TIME; WITH 'TRAVIS APCH'). I FEEL AN IMMEDIATE REQUEST FOR CLARIFICATION WOULD HAVE RESULTED IN A ROUTINE FLT AND APCH; PER THE ADMONITIONS OF OUR PATIENT INSTRUCTORS AND TRAINING MANUALS. LESSON REINFORCED.