Using a cornie keg as a secondary fermenter?

[JD]

So the long weekend saw the first use of the cronies I acquired in last year's group buy. I've racked a beer into a cornie keg and I intend to keep it in there for three or four weeks while secondary fermentation takes place. I intend to ferment under pressure with very little headspace and all dip tubes in place.

As this is my first foray into using kegs, I'm relying on all here to advise as needed. So, is there anything about secondarying in cronies that I need to watch out for?

I expect to have to rack into another cornie for serving. Would it be feasible to carbonate in the same keg without racking or am I just asking for trouble?

What's the perceived wisdom regarding priming in keg rather than force carbonating?

Finally, I'm in need of a CO₂ cylinder, regulator, JG fittings, a tap and beer line. Any recommendations as to places to acquire same?