2000 Jeep Cherokee THREW A ROD: Now what?

My son recently bought a used 2000 Jeep Cherokee with 130K miles. After about 400 miles of problems with loss of coolant, changing the thermstat switch, and adding coolant on several occasions, the engine threw a rod in Salina, Utah.

The mechanic says it will cost $3500 for a used engine, plus parts and labor to install.

What would you do? The kid just graduated from college, and is pretty distraught, as this whole misadventure burned through whatever cash he had. (He had had the car checked out by a reliable mechanic before purchase. But, even though I want to burn the guy who sold him the car, and that mechanic, and the mechanic in Colorado that didn’t diagnose the problem correctly, what’s the use of blame or retribution at this point?)

I need suggestions on what to do. Should the car just be junked? Is it worth repair? Is ~$4000 too much for replacing an engine? Anybody know a reliable and honest place anywhere in Utah, preferably close to Salina (which is well south of Salt Lake)?