trying to combine fireplace with heat pump

hello,



this is my first time on this site. so i hope that i'm posted to the right place.  i'm in a house in Pennsylvania that has 20' vaulted ceilings.  it has become a nightmare to heat.  the existing system in an electric and oil heat pump.  it cost a fortune to heat this house, so we've been using the wood stove in the basement, which almost does the job.  how ever this house does have an interesting feature.  in the living room with the high ceiling, is a fire place.  the rack that holds the logs in the fireplace is actually water pipes.  the inlets for these water pipes happen to reside just a few feet from the heat pump.



what i would like to do is attach a small water tank to one of the inlets and have the other go to a radiator in duct work to the heat pump, then back to the tank.



i obviously have many questions on how to do this.



1.  would i need a circulating pump?

2. what size tank (if any) should i use?

3. do i place the radiator before of after the heat pump?

4. where can i find suck a radiator?

5. is there a brand/model/style i should be looking for?



any help would be nice



thank you