ive been searching for the info online, but cant seem to find it. unfortunately i dont think the pump is able to properly operate under the head pressure of that set up.
generally speaking, powerheads are not meant to push water vertically, so if your sump is under the tank, the pump has to pus the water up 3-4' to go back to the tank. while its rated at 400GPH at 0' head, the higher the water has to pump back to the tank, the lower that number is going to be. even if it has enough power to push the water from the sump back to the tank, youre probably looking at under 100gph at that point.
not only would that give you 2x turnover in your tank (which is by no means sufficient) it will also put excess pressure on the pump motor, shortening its life. if your dad has already put some wear on it, who knows how long it really has left.
but at the same tim, i could be wrong. like i said, i couldnt find the head chart for that powerhead. i would definitely suggest getting that info before moving forward with the project.
as far as what you need to get, it really depends on how you want to set it up.
if youre going the DIY route, you can find everything you need at home depot (or whatever hardware store is near you)
-PVC
-PVC glue
-vinyl tubing
-hose clamps
if you just want to buy the overflow, you can probably get a box overflow from your LFS, and maybe even the hoses to run to the sump. they would also have a roll of mechanical filter pads or filter floss for the top of the drip tray.
so first find the specs for your powerhead to see if its safe to use. then figure out how you want to set it up, and it will be easier to let you know exactly what you need