Make sure its that thick... If its only 4" you can do it all yourself.

Get a drill and verify the thickness. 8" thick, get someone else to
go at it. 4" will only take a few hours and is a good workout.

I broke up my basement floor to put in sewer lines. Not a bad job.

If you want a real clean cut.....
Use a circular saw with an abrasive blade (get two they are cheap)

Put up plastic liners around all the openings and open the window.

A nice fan will be ok in the window

Score it and cut a little bit in, This will give you a nice clean line.

Use a sledge hammer or something similar to break it up.
If you want to make it even nices, drill holes all the way through in
a sort of grid pattern. When you break it up, the cracks will form
from those lines.