1..if you buy DB classic then yes, buy Darkmatter, but if you intend to buy Pro then (IMO) Darkmatter isn`t worth the money just for the models, it`s only worth the cash if you want to upgrade classic with some more features like memblocks and multiplayer.
2..yes, the manual has one "not very good" tutorial, and is realy for reference more than explaining the commands, so if you don`t have any experience of programming in basic then buy the book.
3..you could do it with a map level editor, or you could code the game to make your levels intelligently from a set of rules, you could also hardcode the levels with load/position object commands, but thats too much work for no advantage, so either use a editor or the BSP maps in pro, or get your program to create levels for you
hope that some help, plenty of others will have ideas, cheers.
Mentor.