I'll call the dealer tomorrow to inquire about front weights. These chains you're referring too, are they safety chains or the front and rear guard chains that are already on the cutter?4" is a lot, and you will notice it. I am not a fan of quick hitches for this very reason.
No, the driveline does not include the gearbox but the advertised weight will not include optional chains which will probably add 150 Lbs.
I expect that you will need front weights.