Anthony,
1 - depends upon the size of the memory card you get. If you get a reasonable card size, you can store many sessions on it (sprint races).

I have one card that I'll use throughout the weekend. I've downloaded various sessions to look at them (still working on what I'm looking at) but haven't removed them from the card until after the weekend or sometimes multiple weekends. There's really no need to have two cards unless you're sharing it with someone else.

3 - not sure how long exactly, but it's very quick. Kinda like downloading some pictures onto your computer.

Figuring out how to use the software is pretty easy. That much I picked up on quickly. Since you like the data aspect (that's where I'm pretty clueless right now), you'd have no problems with it.

The only thing I don't like about the DL1 / DASH2 combo is it doesn't have a lap counter. Since often times tracks don't display this info. and haven't had radio communication, I sure wish it did.