The timing window, the hole you have been asking about, does not have to be plugged. Leave it till you get the proper plug. A cork will work but you will probably not bring the right sized one.
Wixom bags are easy to remove usually. If you look inside them you will see some long wire passing through small posts. You lift the wire and slide the bags off the post then lift up.
Seats are often grumpy. Each one has settled into it's own mysterious locking arrangement. If the seat isn't locked, the button is pushed with the thumb and the seat wiggled and raised. They can usually use a little greasing and cleaning.
If the button doesn't push in try the key in it and see if the lock turns then if the button will push in.
/6 seats and LWB /5 seats are identical except for the pattern on the vinyl. Seat hinges can be bent but the OEM ones will usually break.They don't like to bend.