MarketPress Help and payment option

Hi,

I use Marketpress plugin... And I download it and install it.. I have 2 questions:
1) I want to my visitors and customers pay me for products to my master card is this can be done and what Gateway I must use?
2) I have membership on WPMU and I download Market press plugin, my question is can I use it this plugin if I am not member of WPMU, for exemple if I next mount not pay membership?

Thanks