just wondering...if i could use my mac id to charge all the stuff on my account to buy text books..or does it have to be cash/cheque/credit card?

You can use your student card to charge textbook purchases, not your macID. To do that, you have to go to Titles and complete an agreement form before your student card can be activated as a charge card. After that, you'll be good to go the rest of the year.

whats a student card? its totally separate from the macID?

student card = the card you got in the mail with your picture on it
macID = your login information into MUGSI, ELM, etc