To change the name of an account open the register for the account, choose the Moneydance menu option Account --> Edit Account. You can change the name to whatever you require in the window that appears.
You can not change the account type using the standard Moneydance options.
The toolbox extension (menu option Extension --> Manage Extensions to install) does allow you to change the account type where it makes sense to do so. The option is on the Account and Categories menu, and you need to select Update mode before entering the menu. You should always make a backup before using the toolbox options, it will prompt you to do so.