While looking through the grill, locate the hole on the right-hand side and very slightly to the rear of the latch mechanism. Using a thin long-handled flat-tipped screwdriver, coming from right to left at a 45 degree angle, insert it into the hole and pull the handle of the screwdriver to the left in a prying movement. Don't use much force because you don't want to break the latch. It'll pop right open.
This is a common problem with these trucks. A simple way to open the hood requires two people. Have someone pull the release as you simultaniously pull up on the hood. If it doesn't pop, try hitting it on each side a few times. If it still doesnt open, reach in through the grill and pull the release cable maunally. You may need a flashlight to locate the actual cable. Pull it firmly and it should pop open eventually.