Most shops will not just replace the sending unit, they will advise you replace the fuel pump module because there is considerable labor involved draining and removing the fuel tank, and then removing the fuel pump module from the tank after its dropped down. The fuel sender float ass'y is attached to the side of the fuel pump module and this part alone can be purchased for about $60 give or take. However, the fuel pump in your Silverado is prone to failure and even though you have no fuel pump issue now, it is advisable to pay the extra cash (the labor does not change any) and replace the complete unit (the fuel pump module) which comes as a new pump and sending unit ass'y. Depending on brand of the pump it will cost anywhere from a high of about $400 for a DELCO or DELPHI brand (preferred) to a low of maybe $250 for an aftermarket brand like Spectra or Airtex or Carter. Labor will be about $300 give or take. It is advisable that if you will bring this to a shop to have done (advisable of you never dropped a fuel tank yourself) you should ask them to *CONFIRM* that the sending unit is your actual cause. They may add a labor charge for that confirmation, maybe not. I wouldn't if it were me.