Hi Ron,
There are two elements in administering Users:
First you need to have a User Group defined as to what a user assigned to the group has access to. There are 16 pages of options you can assign to a User Group.
There is already a Top Administration set in the original applications and is uneditable and cannot be cloned.
But there is a global select box in the header area that will turn all options on with a single click.
Then once you have your User Groups set up to can assign users to whichever group is appropriate. And yes you can easily reassign a user to a different group. Just select the user, then in the dropdown box User Group you can change their group.
Here's the doc link you need:
http://www.abantecart.com/ecommerce-documentation/51-admin-user-manual/system/usersThe area you need it under System > Users
Lee