Correy,
Dump the grey water right into the san tanks, it will save you a lot of time and clean up, restoring a comode is really easy. Even if you never use your san tanks again the little amount of grey water in the lines will not fill your tanks or hurt them at all.
To restore a comode it doesn't take much to do, unbolt the stool and check for a blanking plate (remove it if there is one present) clean and grease the ball valve and then clean the gasket and reinstall the comode and you are there.
This will allow you to have a honey truck pump your san tank if there is anything in there (doubtful but check)
You might want to review the School of the Boat block on Tanks just to refresh your memory
Darrin