Robert,
You apparently have the DVD Video Player Kit for the Powerbook G3 Series "Wallstreet" M4753.
This is the DVD-ROM module:
http://www.powerbookmedic.com/xcart1/customer/product.php?productid=16219&cat=26 6&page=1
This is the DVD Decoder PC card:
http://www.ifixit.com/cart/customer/product.php?productid=296&cat=&page=1
The above DVD PC card is not Apple's but there were two third-party vendors who also offered a DVD kit...VST and MCE. They all served the same purpose and will all be priced similarly.
Both PC card and optical drive are required to play DVD movies on the Wallstreet, plus Apple DVD Player is only supported when booted to 9.x, not 10.x.
I really cannot give you a fair price to ask; the above hardware prices are probably high but you will get an idea.