"Pop" sound in engine and smoking like crazy
 

I just bought a 2005 Jetta TDi and have put about 1500 miles on a road trip last week, no problems....
But driving on the highway tonight, I heard a loud "POP" sound in the engine and then a ton of black smoke was coming out of the muffler. I pulled it over thinking that the oil might be low, and it was but the oil light didn't come on. I filled it up with the correct oil and started it up again. But, it was still smoking and couldn't accelerate much.
Please help, I am trying to figure this out before I get it towed to a mechanic just in case they try ripping me off....

Caring for the ambiance, anybody is ailing 35