I'd probably got his route if I was going to replace the engine:

http://www.ebay.com/itm/Isuzu-98-02-TROOPER-V6-99-01-VehiCROSS-02-03AXIOM-6VE1-Engine-Long-Block-ILB6VE1-/130954960189?pt=Motors_Car_Truck_Parts_Accessories &fits=Year%3A2001|Make%3AIsuzu|Model%3AVehiCROSS|S ubmodel%3ABase|Engine+-+Liter_Display%3A3.5L&hash=item1e7d861d3d&vxp=mtr

Or something similar with a warranty.