how difficult would it be to swap my 97 ford ranger 2.3 2wd to a 4x4.

 

Easy as pie if you do not mind swapping over to a 4x4 frame and cutting a hole in the cab.

But as you probably already knew before you asked, it is much easier and cheaper to sell what you have and buy a 4x4.

Or just buy a 4x4 to add to your collection.

 

+1, yes not for the faint of heart

4x4 uses a different frame, so starts off different that 2WD
4WD was not "an option" that is simply bolted on/added when a new Ranger was ordered.

But you can convert any 2WD to a 4WD if you have the funds and some welding and metal cutting skills
Ranger front suspension seen here: The Ford Ranger Front Suspension

Frame difference is that 4WD has box frame up front and mounting for front axle suspension

 

I'm gonna be buying a new truck this winter and planned on making a mud mutt out of the 97. I have a 97 4x4 with a hole in the frame the size of my boot so I don't feel it would be good to use that frame can I customize the 2x4 frame or is it a waste of time.

 

Yes you can box the frame same as Ford did, you even have the template in the rusted out frame.