2001 Volkswagen Eurovan What do I do?

I bought a 2001 VW Eurovan used in 2005. It had 40,000 miles and now after several expensive repairs, the mechanic is telling me it has an "incredibly disastrous problem" with the engine - he estimates a $3-4,000 engine repair for the best case scenario and a $8-9,000 for a new engine. We cannot really afford this. What would you do and what should we do?