[the hippie mechanic]

In my experience a die grinder is best for cutting out the rust and a sawzall can be helpful sometimes. The same goes for cutting the replacement metal to fit. Depending on where the rust is you may need a power drill and spot weld bit to cut spot welds in the rocker panels and floors. If you get an air powered cut off wheel make sure you have a pretty powerful air compressor to run it. If you have a small air compressor you will likely get frustrated because it doesn't work as well. Milwaukee makes great electric cut off tools if you don't have an air compressor. Whether you go with air or electric, make sure you get a good quality tool and save yourself some frustration.

For a welder MIG is fine for sheet metal. If you're new to welding MIG is great. Miller has good resources for starting out with MIG as well, and just use the internet to learn. If you're not new to welding you know what you're doing.

http://www.millerwelds.com/resources...ur-skills/mig/