How do i replace the pcv valve on a 92 Chevy s-10?

my truck was running good , but my sister took it and it ended up not turning on so i thought it was the battery or starter or alternator, but everything was all fine. so i opened up the air filter cover and saw oil everywhere, all over the filters and pretty much all in the carbuerator, i tried jump starting the truck and it was struggling to stay on and blew out smoke. i then called orieley's auto parts to ask them what the problem would be and said that the pcv valve neded to be replaced.The only thing is i have no idea where the pcv valve is, or how to replace it. PLEASE HELP!