Nissan Repair: 91 Nissan Truck Timing Chain/Belt, interference engine, mileage engine

Question
My 91 Nissan truck with 186,000 miles broke down today while on loan in another city - to my mother in law.  They had it towed to a shop, and the shop suspects the timing chain broke, but won't know for sure till they get into it.  They are recommending to replace the motor (9.7 hrs + engine) vs. the replacing the chain (6 hrs + $150 for chain) because of the mileage.  Approx $1500 vs. $600.  This is certainly a job I would not attempt on my own even if I had the truck here.  The guy at the shop wasn't sure if it had a chain or belt or whether it was a clearance engine, but suspected it was a clearance-type with a chain.  Didn't exactly make me real confident in him.

Questions are:
What diagnostic would point to the timing chain vs. something else?
Does it have a belt or chain?
Is it a clearance or interference engine?  i.e. with this engine should we expect collateral damage?
Is it worth replacing a high mileage engine with another high mileage engine, assuming we can't get a low mileage engine for a truck this old?

Thanks!

P.S.  She did say it started making some kind of noise yesterday, but couldn't give me anything more specific.  Of course, she ignored it!

Answer
Jared,

If it were me I would go with the replacement engine.  Yes, it is an interference engine and if the timing jumped the valves are toast along with a couple of pistons.  The chain has to be replaced along with the tensioner and if the teeth are screwed up on the cam or crank those will have to be replaced too.  Now, we are not even talking about what the cam looks like.  So, go with the engine swap as it will be cheaper in the long run.  And, if you got 186K out of the first engine you will be ahead of the game and looking at a longer life for the engine.