This is not splitting the atom with Einstein! Did you turn off the electrical? Hope so ... The plate might be held in place by some locking tabs ... but that is rare. Usually, you can access the screws or nails that are holding the fan body in place. Remove those bad boys and you can remove the fan itself.
The unwiring is easy and you should keep the wire clamps just in case. You MUST use wire clamps because vibration can cut the wires in the future and cause major issues. The biggest hassle in a basement is reconnecting the exhaust hose/pipe. The video I found is helpful but they use duct tape. LAME! Duct tape is for many things EXCEPT ducting. Using silver foil tape is more airtight and the adhesive lasts forever.
You should be on your way after reading and viewing this.