93 Cressida - Rod knock

I personally do not have the Cressida but my friend does and is in need of some advice about a possible rod knock. She was told by a mechanic that she needs to replace the engine and that it would cost about $3000, which is how much she paid for the car. I recently asked around and it didn't sound as if it was that big of a deal. Does anyone know about rod knocks and what might be causing it? Any advice you can give is greatly appreciated.

Thanks

Make sure the harmonic balancer is tight.Go checkout Toyota Cressida.com those guys are the experts with Cressidas. O Toyota didn't make a 93 Cressida