No questions are silly! We all wonder most of them at some point...
To join a new ball to your knitting, check out Amy's video on this page: http://www.knittinghelp.com/knitting...iques/misc.php
To knit an afghan, you do need needles as wide as the project, though they can probably be a little shorter - someone correct me if I'm wrong here. You can use long circular needles (knitting flat of course) or you could use 'flex' needles, which are a set of two regular needles with cables that have ends on each (yes, that was clear wasn't it? :? ) If you only have or want to use regular needles, then you could make squares and attach them together to make the larger afghan. A fellow SnB'er of mine, refuses to knit afghans - she swears crocheting is much faster! YMMV
As far as buying a book, it's fun to have one to refer to, but there are tons of free patterns on the internet. Search around and check it out.