Take it back and tell them what you've seen online. If this is a stand-up shop, they will install the correct part N/C. If they do that, just say thanks and chalk it up to a simple mistake like looking up the wrong part (might be one that doesn't get replaced very often). But if they're unwilling to fix the mistake on their nickel, ask to talk to the manager. If they still balk, tell them you're going to another shop and will file a BB complaint against them. Might not work, but there's no way you want to give an outfit that would hose you like that another $ anyway. Just another example of why many of us on these forums try to DIY whenever possible. Good luck - hope they do the right thing and get this taken care of!