By Ralph D. Russo/The Associated Press The opening weekend of college football — the full opener, not the Week 0 appetizer — is a five-day immersive course to get you prepared for an intense and unpredictable 14-week class. The final is due on Jan. 8. Everybody gets an A just for showing up. This season feels like the end of an era in college football, but when the games kick off all the off-the-field messiness drifts away. Week 1 is light on marquee matchups and heavy on potential mismatches. Twelve ranked teams are favored by at least 20 points against…