16V is supposed to be a little more involved
I see them for sale WELL under $1,000. Just saw one for $300 in the for sale section. I see them go, around here, for $300-$700 (this includes ECU, harness & a turn key engine with all accessories). People ask more, but they don't seem to get it sold 'till they drop the price. New economy and all
You're also going to need the speedo (or another speedo) for the VSS, and Buick 318 motor mounts (can't find the part # for the life of me, but should be about $20 for the pair). I honestly don't know what the deal is with the "engine adapter plate" or if it can be bypassed... hopefully someone can chime in. From there, you'll need to spend some time with the wiring harnesses, or send them off to aftermarket4x4 / trail tough / your favorite vendor to have it done for you ($400ish after shipping I think).
If you can have them start it up, and warm it up - you can do a compression test on it. Not sure how useful a "cold" compression test would be? I'm not an expert. If it looks super dirty / gritty, or the belts (especially timing belt) looks cracked & worn - it might have more miles than they claim.