You will see underneath where the rubber feet was, 2 small star head screws which can be removed with a small star head screw driver.
When you have done this the top of the drive can be prised off with a plastic tool or something like a credit card. When you get it started work your way around and it will snap all the clips out which holds it together.
Be very careful when pullings aparts as there is some fine cables that are stuck down the cables can be gently pulled away from the top of the drive. Do not you steel screw driver to prise apart or you will damage and mark casing.
Then at the back off the drive there is a metal sheild that needs to be taken off at this stage you can prise tge sata connector of the pioneer drive and fit BW-16D1HT drive.
Thank you,