There is a Technical Service Bulletin (TSB) for this exact problem. The fix is to tear the engine apart and replace the piston rings. You might have to pay out of pocket for the repair unfortunately. Chevy’s of these model years are known for excessive oil consumption to the point of blowing a hole through the engine block if not topped up frequently. They are lemons.
That doesn’t sound right. Go to another independent shop for another diagnosis, avoid dealerships as you might get a similar sized bill. Research shops in your area via Google, Yelp, etc, good luck.
My opinion, take with a grain of salt:
I don’t know how a fuel pump replacement is over $1k, an OE Delphi pump replacement on RockAuto is $350, I find it hard to believe it’s causing all those lights on the dash. Where is the $650 is labor going to? That can be 5-9 hours of labor depending on the shops rate, which too much IMHO. The pump is under the rear seat, it can be replaced DIY in less than 1 hour, 2 hours if you take your time. Definitely get another diagnosis IMO.