I have a 2002 Jayco Eagle Summit with shower/toilet combo. I also was wondering and reasearching how to drain the gray take for the shower and sewer hook up for the sink. Check this link out. http://www.jaycoowners.com/showthread.php?t=3040
Here you will see my post on the parts/pieces required.
The sink drain should be the lower "water hose" connection on the side of the camper.
I use a short water hose to connect to the Camco 39111 RV easy slip grey water drain adapter. This adaper will connect to a standard 3inch sewer line. This lets you connect to a camp sites sewer and not have to use a bucket.
I do recommend you get one of the slinky sewer hose stands to allow for proper drainage.
In addition, you may not need the Valterra T01-0091 VP 1-1/2" x 3/4 90 degree
posted in the link I provided. Your camper may have a straight connection on the shower gray water drain valve. I just disconnect the sink hose and connect it to the shower gray water when I need to drain the tank. However, I plan to put a "Y" connector and second hose on the Camco 39111 RV easy slip grey water drain adapter to allow me to connect the sink and shower gray water tank at the same time. The only open the graywater tank valve when I need to drain it. This way I don't have to keep disconnecting the hose.
You can contact your local Jayco dealer or Jayco directly and request they send you an electronic version owners. I checked their site and it only goes back to 2003. If you would like you can PM me and I will send you mine so you can compare the differences if you can't get your exact owners manual. It covers how to set up the casset toilet and how to empty it.
Hope this helps