I hope that you mean four foot high fence not four inches high? I will assume that the " means foot to you.
If you are fencing off 350 feet of land and removing all the existing fencing, you have quite a job. My information states that chain link only comes in 4 foot and 6 foot high fabric. Are you sure about the 5 foot?
OK, the labor and material costs for 350 feet of chain link fence should run about $6000. This does not iclude the tear off and haul away of the old fence. So, if we are comparing apples with apples, then you are getting a very good deal.
I would jump on that, but watch out on your contract for cost overuns.