This project is fairly straight forward. You need to completely disassemble both sides including the in sink trims. You will need an adjustable wrench, a large pair of pump pliers or monkey wrench, screwdriver, nothing special. Be sure the electrical wire will reach the new disposal location, it not, you will need a j-box and some wire, you will also need some plumber's putty to seat the drain trims. You definitely will have to replumb the drains and traps, but you may be able to salvage a few pieces. It's gonna take you a few hours so be prepared to spend the day without water in the kitchen.
I disagree with BMitch as far as if the P-trap will come apart. (Possibly the first time we've disagreed?) The metal nut could not be where it is if the joint did not separate. The rest of his answer I agree is the easiest fix. However, if possible, physically cleaning the trap is preferable to a chemical approach. I'm assuming there is a slip fitting just out of the picture, just as there is in non-disposal side. By detaching the metal ring in the first photo and the unseen slip joint, the trap should be able to be removed.
Even without a slip joint, the pipe could be detached right at the disposal itself. This could actually be preferable as it would allow the P-trap to swivel, which may help in loosening the nut. Are you sure you are trying to turn the nut the correct direction? I'm not saying you don't know how to loosen fasteners. The direction depends on which piece the nut is threaded onto, which is not always clear in plumbing.
The curved shoulder of the nut tells me it is threaded onto the U-bend, so the nut is turned anti-clockwise when looking down at it. It's hard to tell by photos, but you appear to have decent access to the nut from the left side as it is below the pipe coming in from the other side. Even though the opposite trap may be in the way for fully turning a wrench, you seem to have enough room to place the wrench handle near the trap and pull right.
As for counter force, if pulling on the pipe itself isn't working, try a large screwdriver wedged in the inside of the U-bend. If you have the right wrench, the ring nut shouldn't offer a lot of resistance.
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You will probably find the right side easier to plumb as there is just more space. Disposals have sort of a weird offset discharge pipe that isn't just a drop in replacement for the existing extension pipe. As you noted the dishwasher piping already runs to the right as well, and that is generally connected to the disposal.