i know nuffin about trucks , but i guess you check for the usual things ...... service history is a must as the 3.1 engine is the best of the engines available ( or so ive heard ) ,
problems ive heard of are ...... fuel pump going ( very expensive )
but in general , parts are quite cheap and easily found
i get my bits from milners off road ,
probably best to join the isuzu trooper owners club too