Open you functions.php
In the getsidebar function, add $loggedinname to the sidebar variable to show the username.
As for the avatar, I think you'll have to edit the logincheck function.
Add this to the last line of the function
PHP Code:
$GLOBALS['avatar'] = $GLOBALS['usersettings']['avatar'];
And add $GLOBALS['avatar'] to the sidebar variable in the getsidebar function