iPad displays wrong user ID
 

I apologize for posting something I know has been addressed, but after registering for the forum I couldn't find it again.

I changed my Apple ID to a mac.com email address. My iPad displays my old ID when I try to update my apps and I cannot change it. I tried logging out and back in, no luck. The new username is displayed in Settings, it's just this window that pops up when I try and update.

I saw other posts that said you can't update something that was bought with an old ID using a new one, but I tried using the password I thought was associated with the old username/email and that doesn't work either.

My questions are:

1) How can I get the password it wants since I now log into Apple with my new username and there is no "Forgot password" prompt on the iPad?

2) Does this mean that if I buy an app on my phone, which DOES recognize the new username and password, when I sync the iPad there will be a combination of apps bought with the old username and pwd, and apps bought with the other? Meaning that I cannot update all my apps at once?

Thanks for any help,

L.