You should check the help information for AMCAS. Contact the two schools directly regarding your interview communication. Ask for a phone call to confirm and receive other advice on the matter.
If you can log into AMCAS still you should be able to update your contact information to a new email address. Do that ASAP, and contact any schools you are waiting to hear from to let them know.
You should be able to login with your old username and password. But do call or email all the schools where you have a pending application. Some of my schools warned me to email them if my contact information changed. So even if you update your AMCAS email, the schools may still send you correspondence to your old email.
Good Luck!
yes. You can just tell them "My contact information has changed and I no longer have access to the old email previously listed on AMCAS. I have updated my contact info in AMCAS and you can now reach me at [new email address]." I would also provide your AMCAS ID/other relevant identifying information. A phone call could also be helpful, especially at places you will be interviewing since you want to make sure you receive all necessary information.