I live in south Georgia and want to run power to my shop but am unclear about the NEC codes.

I have my power fed to the home panel from underground, and want to put 110 and 220 service to my shop that will be approx. 100 ft. total to the shop panel...underground.
As far as space goes in my existing main panel, I have 2 slots left in the panel...2 single pole slots.(or 1 double pole slot)

I am pretty comfortable with the task of running my wires and recepticle wiring but need to know a couple specifics...

1) do I have to come off of the main panel in a certain direction since it is supplied power from the bottom unlike the traditional top fed ?

2) do I have to use some kind of conduit at the main panel inside the house
wall ?...outside my walls ?.... (ie. metal, plastic, PVC)

3) I want to be able to run a small 220v wire fed welding machine along with 6 120v outlets and a 120v air compressor, so what amp service should be enough ?

4) I was told by the "orange people" that I needed 6 guage wire for this feed.....is this O.K. ? (100 ft. from panel to panel)

I am in no hurry to do this project incorrectly so answer when you can as I appriciate all help...

Thanks, Archblast (Mike)
...Despite all my RAGE, I am STILL just a rat in a cage...