@chazz please have a look at this thread PWT disc drive replacement
Also, you need to know the vintage of your PWT to determine if it has an optical drive with an IDE (older) or SATA (newer) interface. The SATA drives are easy and cheap to obtain, the IDE a bit tougher, but also may be more robust? PSA should be able to help you determine which type of drive before you open if you provide them a build date. Not sure if this is true if any updates have been performed on your PWT, but PSA should know that too.
Here’s the optical drive I purchased: https://www.amazon.com/gp/product/B0033Z2BAQ/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1
EDIT: Once you have the PWT open using those funky threaded screws the only somewhat tricky part is removing the front plastic bezel from the new drive (need to open the drawer with a paper clip, etc.) and then transferring the drawer front from the old to new drive. Pretty sure mine was glued on so you need to gently slide that drawer front up on the drawer.