Top of the gas tank is the location. Which has to be lowered for access. As far as cost, that is going to depend on where you buy it and the quality of the pump. I'ld say anywhere from $40-100.
the fuel pump is on top of the tank. You have to drain the tank if it is full and drop the tank to remove and replace the pump. there is a red wire by the a/c evaporator you can run a wire to the battery to check to see if it's working first. My 1999 blazer had a problem with a connector at the fuse box on the drivers side of the engine. A fuel pump will run you around a 100.00 bucks
My 94 blazer had this problem and it was the fuel pump. My Blazer eould start and run for a few seconds and the die,after Ichanged the fuel pump it started reigt up. . Awhile back my truck wasnt staying started for more then five seconds, and it turned out that it needed the RPMs adjusted bc it wasnt high enough to keep the truck going =( didnt cost much though