That guy is ripping you off. It does not take 8 hours to even do a header swap on this car.
Go to RTTuning in Lansdale, PA.
R/T Tuning – Dyno Tuning & Engine Performance Specialists
Talk to Eric the service manager. Great guy! Great shop! Just had my coils swapped there, and they helped me through a small issue and got me on my way. Their alignment/suspension installer is a specialist in Suspension work, that's all he does. And he's good at what he does.