If you paid with a credit card, dispute it.
They can prove what they actually did/charged for to the bank (or get their Visa processing abilities suspended) & the bank will refund you. You pay for this service every time you pay a monthly fee or interest rate - may as well use it.
That said, its a SHITTY job. I've done a few (as an owner not a shop) and I'd be shocked a shop would only charge $500. When I've called around for Long tubes on my Hellcat (which is a far easier install) its always been $1100-1400.
It's do-able as a DIY'r if you're up for a challenge, but I'd expect a capable shop to charge closer to $1000.
Also, while you're in there, change your Opti-spark and water pump.