Are you sure you didn't accidentally ram the forks/FEL/2x4's into something while moving forward to lift the pallet or driving around with the pallet? Or did you try to backup with the forks hung on the ground or pallet? That is a lot of damage and looks more like things were shoved backwards towards the front of the tractor on one side and then bent. I've seen FEL's bent up as bad as this before but it has always been from ramming or hooking something off center with the FEL while the tractor was in motion not just lifting. Most tractor hydraulics stall on a good lift that is too heavy if the tractor and FEL are matched before any damage can occur and before the item can be lifted. I know all of the tractors I have operated popped the pressure relief valve which prevented the lift. Now, my experience is limited to only tractors and excavators that were properly matched to their attachments. We could certainly bend a FEL on the things we operated but you had to ram something or try to lift with just one fork out on the edge or only the side edge of the bucket. We never bent anything lifting a secured load properly. Also, on just a bad lift you usually twist the arms out of square or bend cylinders and mounts. I can't say I've seen a bad lift shove things back into the tractor without the tractor being in motion either forwards or backwards. I mean, heck your brush guard is even jacked to one side from the looks of the pictures (not positive on that). You sure whatever happened didn't bend the tractor frame too?
The following is just my opinion and others will certainly chime in with other opinions. Kind of hard for me to tell from the current photos where the problem actually starts so my advice is to figure out what all is actually bent. If it were me, I would start by taking some measurements along the frame to make sure the frame is still square. If you can't visually tell what on the FEL is bent, I'd start measuring that too. The masts ($??), boom ($1580), and cylinders ($710 a piece) can all be replaced on the FEL. Make a list of things that are bent and price out the replacement parts.
John Deere Parts Catalog Take that price and compare it to the cost of a new 320R (approx. $5000), a used 320R (not sure you can find one), and a quote from the dealer for repair. You might also be able to find a heavy equipment repair shop near you that could give you a quote on fixing just the parts you find damaged/bent. You won't be able to bend the masts, booms, or rams back into spec on your own without the expensive heavy hydraulic machines.
If you haven't worked on a heavy attachment before and decide to do the work yourself, be very careful. It is easy to get a crushing injury or lose a finger if things shift/fall when disassembling something like this. You will need to use bracing and a hoist/lift or a second set of hands when replacing the masts or the booms. Remove the wrong part without the proper bracing and the whole thing could collapse on you. I'm sure you already thought about that but I'd feel bad if I didn't say it and you got hurt.
