Wait........... is it the passcode to update the email? or is it the passcode to unlock your ipad? If its the passcode to unlock your ipad(mine is because of work) then thats not the same as your email password(if you were forced to change that).
Two totally seperate passwords. If you everymonth have to change your email password, that doesnt change to unlock your ipad. That stays the same as when it forced a password lock protection. You just change the email password in settings, mail, (account).
To remove the email from your ipad, you go into settings, mail. Click on the account and all the way at the bottom hit DELETE