Sounds like you need 2 pumps, because your livewell is below the floor.

On my v21 the well is above the floor.
The supply pump is a bilge pump sitting on top of a ball joint shut off valve on top of a bronze thru hull fitting. My box drains thru the side of the hull by gravity since it is above deck.

You probably need another bilge pump to empty your well since it is below deck. I don't know if one special pump can do both in and out, but I would use 2 separate pumps to keep things simple, safe and cheap - but that's just me. ;D

Hope this helps.