how long should it take to replace the fuel sending unit on 2008 chevy malibu

I had gas tank renew do my 2.4 cavalier changed fuel pump sending unit was a component ran me $700 wouldn't have done it but I thought tank was rusty but it was pump .Hope that gives a little insite. The pump and new lines cash and carry were over $500 so I figure get done and waranteed the life of car