Screech does porn, AC Slater hosts Miss America pageants, and Jessie Spano writes self-help books. Yes, Elizabeth Berkley is writing a “self-esteem handbook for teen girls.” Penguin Young Readers Group is expected to publish the 37-year-old’s musings next spring. This one’s certainly a head-scratcher! “Saved By The Bell” went off the air in 1993 — like, when today’s current crop of teens came screaming out from between their moms’ legs. OK, maybe Berkley really is a self-help guru. Still, the whole world has seen her nakeybits in the (not particularly well-received) film “Showgirls,” which may, uh, damage her credibility in some circles.