A Vega, Pinto, or Gremlin that is running is worth $600.
I hope you have bought it already, otherwise it is gone. GO FOR IT MAN, WHAT ARE YOU WAITING FOR. If you don't like it, don't spend a dime on it, sell it for $1500 let them negotiate you down to $1200 and you double your money (less taxes, title, license, and time)
Not knowing if there is a block heater is very odd if the guy knows his car at all and is an MB Diesel aficionado-he should know that-just seems odd-my car has a block heater and I know that.
$600 sounds too good to be true for a running MB D in decent shape. Story is just slightly fishy but still worth a look (I would have bought this thing already if the guy sounded legit on the phone, etc.
Make sure this cat is not like the Ohio Craigslist killer
they lured farm workers one by one to a field to manage crops and used them for target practice.