THE PLT CONTACTED THE ISLAP WEST ARRIVAL CONTROLLER WITH THE INTENTION OF LANDING AT ISLAP, NY. HOWEVER, ISLAP WAS BELOW MINS, SO THE PLT DIVERTED TOWARD FARMINGDALE, NY & ASKED ABOUT THE WX THERE. THE ISLAP CONTROLLER COORDINATED THE DIVERSION WITH THE FARMINGDALE/REPUBLIC TOWER & TOLD THE PLT TO EXPECT A BACK COURSE ILS APCH TO RWY 32. ALSO, HE TOLD THE PLT TO CHANGE TO NY APCH CONTROL & SAID THEY WOULD HAVE FARMINGDALE'S WX & WOULD PROVIDE VECTORS. THE PLT CONTACTED APCH CONTROL, BUT DID NOT INQUIRE FURTHER ABOUT THE WX, NOR DID APCH CONTROL PROVIDE IT. THE CONTROLLER VECTORED THE PLTTHRU THE LOCALIZER, THEN BACK TO IT. THE PLT WAS CLEARED FOR THE APCH & WAS INSTRUCTED TO CONTACT THE TOWER AT 1 1/2 MI FROM THE FINAL APCH FIX (FAF). HE HAD DIFFICULTY TURNING ONTO THE LOCALIZER & BEGAN A MISSED APCH APRX 2 MI AFTER PASSING THE FAF. HIS INTENTION WAS STILL TO LAND AT FARMINGDALE. HE WAS INSTRUCTED TO CLIMB TO 2000 FT & WAS PROVIDED VECTORS FOR ANOTHER APCH. HOWEVER, HE DID NOT MAINTAIN ALT & SUBSEQUENTLY CRASHED IN A MARSH. NO PREIMPACT FAILURE FND.