Damaged left front end

Would it be possible to post some pictures of the truck from the front and sides and under the hood? That would make it easier to see what is really damaged and needs to be repaired or replaced. From your description it sounds like at a minimum you need the left fender, inner fender, core support, bumper, hood and possibly the frame straightened as well. Then there are the various wiring harness pieces and other under hood parts.
As for how to guides, you would be better off looking online at places like YouTube, NICOclub.com or possibly a Haynes manual as the factory Nissan information isn't very detailed and doesn't even show items like fender removal.

Yes, certainly I've removed the fender skin. But damage is pretty extensive on driver's side front. Without a torch I see no way of pulling it out.

There is no structural damage this was a rear end collision at about 20 mph. Swerved to miss him but clipped his right rear bumper. No damage to his auto at all. No report even made.

I just need to know how that front end bolts onto the frame. The cab has four main supports sitting on rubber bushings. I'm wondering if that front clip bolts on like the cab does.And if it would come off in one piece. I have seen this before where someone has a complete front end removed and for sale. All the wiring harness would have to be detached for sure but that's not a big deal. The wiring is all intact no damage. It's just that fender frame work I guess you'd call it. Is crimped pretty good and without heating that with a torch there's no way to pull it back out. Even a heavy duty come along.

Yeah, for that damage you are going to need a body dozer or frame machine to pull it straight. That is done without using heat by the way. Heat causes the steel to stretch and deform in the wrong places and you can easily tear the panels apart if they are hot. There should be two bushings under the area of the radiator where the front bolts to the frame. The problem is that it is all a welded assembly. The cab and front support clip are all one piece. The fenders hood and trim are bolt on, the rest is welded as a unitized piece. Repairing it means drilling out the spot welds of the damaged parts and welding in replacements. What you could do is remove any bolt on pieces then see what a frame shop would charge you to pull the damage (if you have one that still does that work).
Or buy one of the porta-power type units from harbor freight and use it with some solid anchors (trees work if they are big enough) and pull it back into shape. Want a good place to see this type of work before you start - go to arthur tussik on YouTube. He is real good at drilling out welds and straightening steel using a lot of the older methods before all the computer machines and fancy frame racks took over.
This link gives the various dimensions of the parts and the frame mounts so you can see what has moved.
https://nicoclub.com/FSM/Hardbody/1997_D21_Truck/bt.pdf
Sorry I'm not more encouraging but Nissan didn't make them easy to repair without a lot of tools.

Your right but that is some awesome information. Thanks for the great ideas and I will go to Harbor Freight tomorrow. How big of a rig you think I should need? Actually is just the fender insider the engine compartment. Where the skin bolts on that's the problem. The front radiator support can be replaced. Thanks very much for your input. JC

I would get the 10 ton, they also have a pull back ram that would be helpful if you use anchor points to do the pulling. You can always move the handle slower to slow things down and reduce the pressure but if you run out of power on the 4 ton you cannot add more.

How much air pressure would it take to run these tools?

None, they use a hand pump like a jack and use hydraulic pressure.

Okay, I see they start around $140.00 great idea. Makes more sense to try and straighten it out and just buy a fender and hood. A lot cheaper than the other way. Thank you for your help.. JC

I would straighten as much as possible. You could always go to a salvage yard and buy a section if needed as well. Either way thank you for using 2CarPros.

Thanks Steve for the great suggestions and ideas. I watched a video last night of the latest in body straightening and frame work and they have this really cool tool now called a little duke they showed live videos of the thing at work and it's truly amazing. it uses a three point cable and attachment mounted on a rolling dolly like frame and it's motorized with a hand held control box. Check it out if you have not seen this invention. Thanks for your help. JC