what is the function of the sending unit on a GMC1500 Sierra on 2006 GMC Sierra 1500

I had P0449 code - shop replaced canister vent solenoid & vent valve - now have non-working gas gage - could this be due to bad sending unit? Shop is saying gas float is to blame, need new fuel pump - what is connection of sending unit to gas float ? pls advise

1 answer
return for poss warranty issue,they may have caused issue depending on previous work preformed