2002 V6 "Broken Engine"

[RJLipscomb]

My brother's 2006 VG Sport Trac has a problem:
He drives as if Ms. Daisy consistently sits in the back seat. Never misses an oil change or rec'd maintenance. However, driving on I-95 the other night he says it starting losing power and a couple of minutes later the check engine light started flashing and it the engine started "rattling". He pulled off the road and called me.
I went to retrieve him and expected the fan belt (from his original description of noise). Checked the fan belt, ok; oil, ok. He started the engine and it idled extremely rough and had a loud "rattling" noise on the upper rear left side. No loud clunking, no apparent backfires or exhaust pops. He turned it off and we went home.
Next day, towed to his favorite Ford Dealership, they say the engine has something broken internally. Needs a new engine, $5,700 (KBB Trade in by coincidence). I'll bring it to my house and start tearing it apart.
Any thoughts on possible issues?