380SE died this morning...

I'm thinking it's pretty serious. There was a little pop and hiss from the left front, almost like the sound was coming from the wheel well. The radio was on so I wasn't able to hear anything all that well, but I even thought for a second the tire blew out. I was lucky enough to get the car all the way off the road and I opened the hood; there is a nice little crack, maybe 4 inches long, in the head cover, and a little oil has leaked out of it. Any ideas on what the problem is, cost to fix, etc... would be appreciated.