Holy Crap What Went Wrong!

OK ... i have a 1971 buick skylark GS. I was driving the other day and while i was getting on the freeway my car would not shift from 2 - 3 it was just giving me really hing revs.:eek2: so i pulled over and when i did the engine cut out. i tried to start it again but got nothing just cranked over and over like the battery was dead.
The next day i got it started and i heard the rocker arms rattling loud! Its also begun to leak oil I have no idea whats going on or where to start!

ANY IDEAS!!!!!