Code:
wknum=$1
new_dir=week$wknum
Re your 'specificity' qn, out of all the things you've been recommended (all good btw) I'd say Rute guide is prob the best tutorial for beginners as far as example progs go. Some of the the otheres tend to just show individual techniques ie more of a ref than a tutorial. Nonetheless, have a look at them all and borrow bits as they suit you.
Also, in general, don't try to solve an entire task all in one go, break it down into small bits that need doing and play with cmds to just do each bit, then put them together later.
This is an HTML version of the man (manual) pages; easy to search
http://linux.die.net/man/