I don't like the looks of that. You could have a small compression leak into the cooling system. Get the HC test. The Block Tester (the one the 3rd Napa store suggested) is the one I've used. It works. If you don't like other people touching your stuff or if you think you might be doing this again someday, then that might be the way to go. If you trust the shop and don't care to ever do this again then I'd probably just pay them to test it.