You don't need a soldering iron to swap the kickstart roms in any Amiga model. They are socketed, so all you need to do is open the Amiga's case, take the metal shielding off from the top of the motherboard, use a flat head screwdriver to carefully remove the existing kickstart rom, and then push the replacement rom into position.

A very easy upgrade to do.

You can even connect up something called a rom switcher that would allow you to have more than one rom installed, and switchable at bootup. 3.1 and 1.3 rom combination is a popular one, for running never Workbench, but with compatibility for older games. Our member Amigamaniac manufacters rom switchers if this interested you.

I would howver just hold out until you find a good condition A500 with ks1.3 roms. It is much easier, and probably cheaper than buying one with the wrong rom and then trying to located a 1.3 rom to replace it.