Are there screws on the back plate that the terminal posts are on? If the screws are there unscrew them and pop the plate out, then you will have access to the terminal post. I replaced a 4 on the Mission speakers I used to have with no experience and to be honest it wasn't difficult. A flat stable surface is required and only remove the screws that are holding the plate to the box.
I've just checked my current set (see sig) and the screws are in the terminal post plate as well. I think it would be very strange to have to remove a bass driver on the front to replace a terminal post on the back especially if there are screws on the plate.
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