Sorry you had a bad experience at the dealer. It's a real shame they allowed someone with no real training to work on your Corvette. The service manager is also to blame for letting an untrained worker do an oil change on a Z51 equipped engine. There are many horror stories about screwed up oil changes on the Z51. I know two people that had their engines overfilled.
I do all my own oil changes even though GM gives you four "free" oil changes in two years. I have access to a car lift and I'm happy to spend the money for the oil and filter and know the job was done correctly.
With dealers it's all about the money. They put people on the oil change line with little or no training and rush them so they get as many cars in and out as possible. You're lucky if they put down the paper mats down to protect your carpets. I won't let a dealer touch my car unless a warranty issue forces me to.
