I know of course it's a different car, but this is an exceptionally common repair on aussie mopars, because when they built them, they used the US spec A body floorpan (more or less) but moved the steering box from the front K-frame (crossmember) to the chassis rail, and they tear the rail out (sometimes completely) either side of the steering box. They also can have issues of rust adding to it (sometimes the passenger side goes too near the idler arm).

If you look on aussie mopar forums - like moparmarket.com for example, there should be info on those repairs from start to finish. It would make a good introduction to what is required etc.

DUY with your own mig is definitely a good option, but I'd make note of how special these cars are, and the fact that some of the hobby level mig welders (even from reputable brands) just don't cut it. The bigger ones (probably nothing under around 160 amp in Aus) are not just better due to ability to work on thicker material, the 'larger' ones almost without exception have better transformers and astronomically better wire feeds and so forth..

If you want to do it, get a bunch of scrap metal and practice practice practice first.