2000 ISUZU ISUZU TRUCK Engine And Engine Coolingengine Problems

IN DECEMBER, 2005, I NOTICED THAT MY ENGINE WAS KNOCKING. UPON ARRIVING HOME, I CHECKED THE OIL. IT WAS BONE DRY. I HAD JUST REPLACED THE OIL 4,500 MILES BEFORE, AND CHECKED THE OIL 3 WEEKS PRIOR TO THIS PROBLEM. I REPLACED THE OIL AND THOUGHT ALL WAS WELL. I WENT TO WORK THE NEXT DAY, AND STILL HAD A MINOR KNOCKING. AFTER LEAVING WORK, I WENT TO GET GAS. UPON ENTERING THE GAS STATION, MY TROOPER SHUT DOWN. WHEN I RE-STARTED THE TROOPER, THE ENGINE HAD AN EXTREME POUNDING. I HAD IT TOWED TO MY MECHANIC. RIGHT AWAY, WITHOUT EVEN LOOKING AT THE ENGINE, MY MECHANIC TOLD ME I HAD BLOWN MY ENGINE. WHEN I ASKED HIM HOW HE COULD TELL BE JUST SIMPLY LISTENING TO THE ENGINE, HE HAD TOLD ME THAT HE HAS SEEN ENOUGH OF THE TROOPERS AND RODEOS TO KNOW THAT WAS THE PROBLEM. I...