Filling in pool - need educated

[swanny]

Customer has a 16x45 pool that's 9' deep sloped to 4' deep that he wants me to fill in. Has 4' concrete walk around it.

I'm figuring I'll have to take my saw and cut a 3x3 square out of the deep part to allow for drainage. Adequate enough? Too big, too small?

Anyone ever done these? Not sure how tough it's going to be to lift up the sidewalk and neatly stack it in so it won't settle, but that's the plan.

Access is easy...guess I'll fill the voids with stone, bring in topsoil, rake it out and seed/straw the area. I'm thinking between $3 to $4k for the job. Too expensive or cheap?

Thanks for the input!