Yes, 'personnel', as a collective noun, can mean 'staff', but I wouldn't say that they are always interchangeable. 'Staff' are employees, but that isn't always the case for 'personnel'.
In fact, the commonest collocation with 'personnel' is actually 'military personnel'. We use 'personnel' in this context for the body of people who work for an organisation (i.e. the army) in professional capacity, but who are not employees, as such.