No Start

[bikernut]

My 2003 GMC 3500 4x4, 6.0 engine with auto trans won't start. I shut it off and went to start it later to move it and it just does nothing with the starter. I have all my lights, gauges inside as well as lights outside. The dump body works fine. I did check the batteries and found one defective so I went and purchased a new one but that wasn't the answer.
I checked to make sure the neutral safety switch hadn't loosened up and moved but it still won't start in any gear selection and putting the vehicle in reverse the back up lights & back up alarm work when in the R position on the selector. I have gone under and taken a hammer and rapped the starter to see if that worked with some one turning the key but again no start. The solenoid doesn't even click. I tried to purchase a solenoid but you have to purchase the whole stater assembly, and they cost $412 at dealership but my cost with discount is $303 still big bucks.
I looked in the electrical fuses to see if there was a relay or something that was bad but didn't find anything but maybe you fine folks have had this happen to some of you and can point me in the right direction before I spend $ for a new stater.
thanks for any help you can send my way.