looking for advise

Hello everyone, I'm really glad to have found this forum. I was quoted £600 to replace a fuel injector on my Mercedes E350 2009 V6 I've decided (or rather been forced) to attempt the repair myself as money is tight. After doing some research, I feel fairly confident about the process except for...

I am thining about buying a 1988 260e. It had 2 owners and the second one passed away. It was Chrysler certified for the sale to the second owner. The catch is it has 220,000 miles on it. I have drove it several times and it runs great. The only thing i see is a slight oil leak from the valve...