Should I make this purchase ('88 420 SEL) He needs to know tomorrow!

[ericzacha]

Hi all,
I was running thru craigslist when I found this ad

MINT CONDITION MERCEDES WITH NEW FACTORY STRUTS WORTH $1200, $800 PERELLI RADIALS WITH LESS THAN 6,000 MILES. CHAMPAGNE PAINT JOB LESS THAN ONE YEAR OLD. TIMING CHAIN BROKE AND DAMAGED ENGINE. OTHERWISE, EVERYTHING ELSE FROM AIR CONDTIONER, TO POWER WINDOWS TO AIR BAG IN EXCELLENT CONDITON. $1100 OR BEST OFFER.

I went and saw the car and it is as described. Offered him 700 over the phone and he said yes. Told him I need a day to think it over. So what do you think? I own a '88 300 SEL. I was originally thinking of buying it as a parts car, but the body and interior are in such good shape that I'm wondering if I shouldn't just try to fix it up.
My car needs new tires. If I swap the Pirellis to my car, I get about 300 dollars worth of value. I ought to be able to get 400 dollars worth of value out of a car with top end damage in otherwise good shape right??? Then I've at least covered my expense. I'm just a student, so 700 dollars is a real amount of money to me, but I do love these cars. Please be brutally honest. Thanks, I trust your opinions.