Hey y'all, I'm new here, just inherited a 2004 chevy blazer 4dr 2wd 4.3l vortec. This blazer has been sitting for about 4 years and was never started. I got a new battery and fresh fuel. I am mechanically inclined, just don't work on newer vehicles or chevys. I am not sure where to start. It turns over and cranks and will fire for a second on starting fluid. The security light is constantly flashing as well. Any advice would be greatly appreciated, mahalo.