Hi Hanson,
As to the first question, I would say shoot in RAW anytime. It gives you far greater control over the outcome. If you would use RAW or jpg in PowerDirector depends. I never used RAW photo material, so I wouldn't know too much. I know PD can import RAW files, I don't know how much control it gives you in manipulating them. In any case RAW gives you more flexibility to (if needed) create better jpg's for use in PD.
As to the technical side of actually capturing it with a photocamera, the link below leads to an extensive tutorial on how to best capture them. It's from 1999, so it deals with film and not digital images, but many of it that involves f stops, shutterspeeds and the like still holds up today. It's on a website dedicated to eclipses so you might find more useful info there:
http://www.mreclipse.com/Totality2/TotalityCh12-1.html
You may also want to consider using a videocamera capable of timelapse recording if you have one. Or use both a photo- and videocam if possible.
Sadly I live across the Atlantic so it won't be visible here.
Last peace of advice: In addition to making the shoot, don't forget to also enjoy the event itself
regards, Frank