It should be relatively simple and standard. If the D500 supports the Dial-Up profile (which it should).
Once paired with your PC, configure the bluetooth connection (from the PC side) to enable Dial-Up Networking with your paired phone. This should add the phone as a Bluetooth Modem.
Go into Network preferences, create a new dial-up connection. Pick your new Bluetooth modem as the modem.
When prompted for a username and password don't enter anything. The number you should enter as the telephone number is:
*99***CID#
Where CID is the internal connection ID of the Internet.GPRS connection. You can find this by going to your data accounts on your phone, viewing their details / editing them. It should be able to tell you what the CID is.
Then just dial-up as you would normally do from the PC.
****NOTE: These are the |generic| instructions. I am familiar with the D500 at all, but this *should* work. The D500 should support the Dial-Up bluetooth profile, but it IS Samsung's first Bluetooth phone, so it might not be there. Then you will need the USB data cable.