Flat head screwdriver goes in the end of the bulb

 

I'd try a junkyard for the light. There's a bunch of Blazers in them nowadays. Did you get your fuel leak fixed? Could be the "O" ring that seals the fuel sender/fuel pump in the top of the tank or if you're lucky just the hose that connects the filler pipe to the tank. Hope it's not one of the fuel lines.

 

You need the light assembly or just the bulb?