Yes, a freezer converted into a kegging setup is called a keezer (keg + freezer = keezer).
1/4" barb is fine, i'd venture to say that its what most of us who use barb fittings use. I use 3/8" line on my 1/4" barbs and just tighten it down real good with the worm clamps to seal it. The gas line is what I fiddle with the most, and using a slightly oversized line makes it easier to get on and off.
Elkins Creek Brewing Company
Secondary: Bavarian Hefewizen (extract)
Bottle: Blue Moon clone, Sam Adams Boston Ale Clone, Christmas Chocolate Stout (All Grain)
Keg: AHS West Coast Pale Ale, BierMuncher's Centennial Blonde (All Grain)