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How to operate toilet and sink 2013 2400 OB

I apologize for length. Just frustrated, and inexperienced and need help

I recently purchased a lightly used (100 hours) 2013 Hurricane 2400 OB, and I do not know how to properly operate the toilet or the sink in the head.  Waste in the toilet remains in the lower portion of the porta potti, and the sink does not dispense water.  The wash down at the stern, the livewell, and the hose behind the helm work correctly. The previous owner was elderly and never used the head, as it takes some contorting to get in and out of.
From my internet searches, it appears as though the toilet is a Thetford Porta Potti 320b.  Which would mean that it is removable as a unit, and I simply dump it in the nearest approved area.  However, there are tubes coming out of the back of it that travel into the hull somewhere.  This makes it impossible to remove without undoing hoses and creating a foul mess in the head.
Additionally, on the helm, is a Vac/Flush switch. From what I can tell, it does nothing. turning on and off makes no noises, sparks, or smoke signals. Also, there are no switches in the head indicating that this an electric flush head.
I have placed water into the upper holding tank of the porta potti, and flushed water into the lower portion of the porta potti.  Afterwards I have sucked out the water by attaching a shop vac to the waste outlet on the gunwale.  So, somehow, someway the water is moving from the porta potti into the shop vac. Meaning, that the system is sealed and I can create vacuum to remove the waste
Is there an additional fresh water tank that I need to fill to operate the toilet and the sink in the head?  I have filled the fresh water tank that the washdown hose at the stern and the sink faucet behind the helm use.  They work when ever I turn on the fresh water switch. 
I guess really, I need to know what type of system I have and how it is supposed to function so that I can even begin to troubleshoot it.
This is my first boat toilet, and I have 3 girls that would like to use it.
Thanks for your help.