where is the fuel filter located

It appears that the fuel filter is located in the fuel tank on the fuel pump/sender unit. Although I do not have an Isuzu owners manual to refer to (if you have one - defniitely check it...if you do not, it would be a great idea to obtain one...), I would suggest that the fuel filter is not a normal maintenance item, and would not think to replace it for normal wear and tear at your mileage.