If you have some basic metalworking skills, it's not too hard. Just cut until you have clean metal. If you want to retain the original contour, use a hammer and dolly to create a concave patch. Otherwise, just roll a piece of steel to match to general curve, cut it to match the hole and weld. The only trick if you do this is to extend the jack tubes, which is easily done by welding a piece of 1" plumbing to the end of the existing tube. As long as the welds are reasonably good, strength will be preserved.
One thing I would suggest is to never weld OVER the existing metal. While it may seem that two layers of steel are stronger than one, that's not the case.