Regarding 1):
I would recommend extensively browsing these forums while you wait for DBP to arrive, specifically the "darkbasic pro" and "newcommer's corner" boards. Also check out the online help sites to get a glimpse into the command set.
Download the trial version, play with it, try the tutorials, change the tutorials and see how it affects the program.
It is good that you already have some programming experience, especially experience with BASIC. Some of your favorite BASIC commands are a bit taboo in DBP though, such as the INPUT and GOSUB commands, many people frown on using them for good reason.
A tip for using the forum: Ask programming questions here on the forum only after you have searched for the answers yourself, everyone here gets anoyed at people who don't even try to find the information themselves, because we end up repeating ourselves over and over.
At the time of this post, DBP isn't bug-free, the included help file is horribly out-of-date, and you're definately going to experience growing pains as you learn the language, but I wouldn't give it up for anything else b/c the power it gives you and the relative ease of coding compared to alternatives outweighs the bad side.
That's my two cents, welcome to the world of DBP