Shared mailbox setup

My co-worker and I both need to be able to have access to the same mailbox with the following conditions and need to know the best way to set it up (i.e. a Public Folder mailbox with restricted access or as a regular shared mailbox.)

We both will need to be able to send from this mailbox address (with the From: field showing it was sent from the mailbox’s address NOT our personal mailbox).

We also want the items sent from it to appear in its own Sent Items container ( not our personal ones).

Need to be able to manipulate the folders and messages associated with this box.

Any suggestions would be appreciated.