Not experienced enough to remove the movement, might have to be a watch shop jobby.
This is a simple step by step guide on how to remove a 7S26 movement which is what is inside your Seiko:
http://www.watchfreeks.com/115-watch-movements/17659-diy-how-remove-seiko-7s26-movement.html
@Soul started
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This is a simple step by step guide on how to remove a 7S26 movement which is what is inside your Seiko:
http://www.watchfreeks.com/115-watch-movements/17659-diy-how-remove-seiko-7s26-movement.html