Resource mailbox

1 --- I need to set up either resource mailbox or shared calendar named "Time Off", so that our departments can send  Time off taken by their employees. All department employees should be able to see the calendar, and only Department Mangers should be able to send the appointments.
I need the appointments to remind everyone through reminder popup 4 days before an employee takes their time off.

2--Another thing that I want to know about calendars is , how do I know if someone is in a meeting or taking time off without going through step 1  above? Cannot I just create new appointment add a user as an attendee, and this will display their free/busy time ? then close the appointment without sending it ?

Thank you