Liz: From what I understand any brand of SM card will be fine. I'm still looking for a 128 MB one in Canada as the shipping from the US is more then the card sells for.
I buy all my books from Fictionwise and they do take Paypal. They also have (in the multi format selection) OEBFF Half VGA (IMP) which is the format you want for the EBW 1150.
AS for secure books... Spend some time on google and you can find various tools to format shift those.