1996 camero shakes

I have a 96 chevy camero and it has had the abs sensor light on for awhile my fiance never fixed it before he was deployed overseas. Anyways the car has been shaking between 60-70 mph and whenever I apply a lot of pressure to the breaks like getting off the freeway or going down a steep long hill. He says its because of the abs sensor and a friend of mine who checked it out said it was the roaters, allignment, and shocks. I have no clue. I just cant afford to spend a lot of money and I dont want to take it to a shop to have it plugged into a machine for the abs sensor if thats not it. I heard it was like 80. Just to find out about the abs thats not even for a part or repair, please give me your imput on what I should do.