timing chain tensioner

Hello all. Thanks for your help in advance - I'm at an overseas base and don't have any real qualified mechanics to help me diagnose this problem, and I'm just a shade tree mechanic, some top-end/cylinder head/intake/suspension/transmission jobs being the extent of my experience. In short - one day, the 2002 Ford Escape with 3.0L v6 Duratec (101k miles) started making rattling noises from the engine. Sounded like a loose pulley, but there were no loose pulleys, so assumed it was a bearing going bad on one of the accessories. A few days later, was unable to start it anymore. Engine appears to have seized, yet it never overheated, oil looked fine, no metal in the oil, etc. There were never any warning lights. It ran one day, next day could not get it to turn over without an overbearing amount of external power applied via one of those large rolling shop battery stands, then eventually even that wouldn't turn it over anymore. Tried lots of the typical stuff. Cannot even turn it by hand with a wrench on the crank pulley and the spark plugs out (and they all look good). Took off the oil pan below and valve covers on top. Nothing looks out of the ordinary. Doesn't look like any valves dropped or anything, but I wonder if the timing has somehow jumped out of sync - the timing chains look okay, and seem pretty tight, but that seems to be the only thing left. Any suggestions?? Need help! Or at least need to confirm that the whole front and top end of the engine are going to need to come off.