Say I have Donate Now buttons on my blog and it goes to my paypal account to donate. I changed my primary email on my paypal however, my other email is still in the data base... Does this mean anything sent to both my emails, payment wise, will still end up in my account? Or do I need to change all my payment information to my new email address?
When you create the Donate Now button, it would be associated with the email which you log in with to create it and that is where you will get the email in regards to any incoming donation. If you removed that email address, you would need to recreate the button or change the parameters to support it. However if the email address is still in the database then you do not need to do anything.
As eddy said, as long as you only changed primary emails, and didn't delete the old one, it should be fine.