737-300 DOES NOT COMPLY WITH DEP PROC THEN FAILS TO LEVEL OFF AT ASSIGNED ALT.

Narrative

FLYING A B-737-300 ON THE LAGUARDIA 6 WHITESTONE CLB DEP I FAILED TO START A REQUIRED L TURN TO 040 DEGS AT THE 2.5 DME FIX LGA VOR. I REMEMBERED THAT THIS DEP REQUIRED A L TURN PASSING 205 DEGS. I STARTED A L TURN AND COMPLETED THE DEP. CLBING THROUGH 15000 FT THE COPLT SAID 'LEVEL OFF.' I FLEW THROUGH THE ASSIGNED ALT AND IMMEDIATELY LEVELED OFF AND RETURNED TO 15000 FT AGL. THE MAX GROSS WT TKOF AND DEP WERE WELL BRIEFED. A 19 MIN GND DELAY WAS ENCOUNTERED THAT INVOLVED CONTINUOUS TAXIING TO ACCOMMODATE OTHER GND TFC. PREPARATION FOR THE BLEEDS OFF TKOF WAS DISTRACTING AT THE LAST MOMENT BEFORE TKOF. EVEN THOUGH I HAVE FLOWN THE NEW YORK DEPS MANY TIMES; I SHOULD HAVE TAKEN TIME TO REVIEW THE DEP AGAIN PRIOR TO TAKING THE RWY. WHEN AIRBORNE I GLANCED AT THE DEP AND WAS MISLED BY THE CLOSELY SPACED FLT PATH DEPICTION OF THE VARIOUS DEPS ON THE LAGUARDIA 6. I INITIATED A TURN THAT WOULD HAVE COMPLIED WITH THE MESPETHE CLB; NOT THE ASSIGNED WHITESTONE. I WAS REVIEWING MY POOR PERFORMANCE ON THE DEP WHEN I FLEW THROUGH MY ASSIGNED ALT. I SHOULD HAVE PUT THAT ERROR BEHIND ME AND DEVOTED MY FULL ATTN TO FLYING THE ACFT. PERHAPS IT WOULD BE HELPFUL TO ALL PLTS TO EXPAND THE LAGUARDIA 6 DEP TO 2 OR 4 PAGES; DISPLAYING THE DEPS IN A LESS CROWDED MANNER. DEPS COULD BE DISPLAYED BY RWYS OR PERHAPS BY DEP DIRECTION SUCH AS N; S OR W.