New here, 1st Jeep on Friday plus 4.0 help

The guy I got it from is our mechanics instructor, he initially thought it was a bearing knock and replaced the crank and bearings but rattle still there. Kinda comes and goes.

Two questions I have no answers for about wrist pins:

1) Could a bad wrist pin still be tight enough to not be noticed while changing the crank bearings?

2) Can the sound of a bad wrist pin randomly come and go?

I figure that while under there he did check for cracked or broken piston skirt(s) and there were none, so what the heck, here's some questions specifically regarding this Jeep:

Has the Jeep been driven with this condition, if so how long? How far?

Or was it just parked after the crankshaft and bearings were replaced because of this?

What weight of oil is in there?

Can we trust the current oil pressure gage? With the "comes and goes" issue I'd like to see what a mechanical gage says at EVERY given moment.