If you can MIG mild steel you should find stainless OK. It seems a bit more spattery and the welds don't end up quite so flat, but everything else is similar to mild steel.
Apart from the wire obviously. You'll need to use stainless wire. If it's food use then Hitachimad suggests 316 wire: http://www.mig-welding.co.uk/forum/showthread.php?t=334&highlight=316 And the shielding gas which should be pure argon. (or if you are me doing exhausts and aren't too fussy about appearance (and possibly strength) you could use an argon/CO2 mix).
One thing I've learned on this forum is not to tidy the weld up with a mild steel wire brush. That leaves a coating of mild steel on top of the stainless which rusts and looks horrid.
I find Arc is good on stainless as long as you are working thicker than 16g. Stainless rods strike and flow better than mild steel ones especially at the lower settings.
Alex