Head over to google, Log into your youtube then click account.
Click on the "security" tab and change all the info make sure to add two step verification for best security.
Changing the primary email
___________________________
This is were things get tricky and take awile.
First head over to
https://support.google.com/youtube/contact/linkissue
Answer all of the basic questions on the page. Full name, YouTube username & contact email address.
Make sure you use the email you log into your youtube with as your contact email to make things 2x faster.
Once you have finished filling everything out, go down to "Please select the issue you're experiencing" and click "Other"
In the "Describe your issue here" Box put the following:
Hello! I'd like to unlink my YouTube from the current email address to change it to one of my other emails. Can you please help me out with this? Thanks!
Then submit the ticket.
You should get an email within 24 hours asking if you would still like to make this change reply to the email saying you still would like to swap your email address.
They will then email you back telling you they have changed the password to something random, This is were you log into youtube with the name of the channel(Not the email) and your new password.
You can now swap the Gmail! Once swapped the password will be the one on the gmail account you linked the name to not the random password they gave you.