if you have two paypal addresses, how do i know which one is ebay money is going in to?

Pull up the sell-your-item form (you can pretend to sell similar on an existing auction and then not post it) and scroll down to the payment section. The email address shown is where the Paypal payments will go to.

Note, both paypal accounts must be in good standing and the one you use to receive money must be either a Premier or Business account. Anything else is in violation of policy.

PS, I did something worse once. I hadn't sold in years and went to list several items. The email address on the SYI form is phantom data (held over from the last time I'd sold) and belonged to an ISP that no longer existed. I had deleted the email address from my Paypal account and discovered too late that once an auction has ended, you can't cancel or fix it...and if the ISP doesn't exist, you can't link the email address to the Paypal account because you can't get to the confirmation email.