Just attach your intake tube from your cannister to the overflow and then attach the return from your cannister to the return hole. You might have to get some reducer couplings and whatnot from Home Depot or whatever, in order for the cannister tubing to fit properly.
If there is no return hole, you can just send the return of the cannister up the back and over the side.
Should not have to drill anymore holes. But if you already have a sump, why not use that? I much prefer sumps and overflows to any cannister or HOB power filter. And that Iwaki pump is a beast. I would certainly incorporate that into my system.