1) Yes, the ClassiPress Ultimate edition licence is WordPress MU enabled, so this would be the relevant option you would want to look at purchasing.
2) You can actually use Paypal for credit card purchases without the need to have a Paypal account. I believe you need to set up a certain type of account for this link to be available, but it looks like the screenshot below:
http://appthemes.com/wp-content/uplo...-cc-option.png
Also, if you weren't aware, the latest release of
ClassiPress, 3.0.4, now includes a bank transfer gateway so your customers can pay this way too.