If it does, here's where something will go sideways. It's all in the details:
- Not cleaning enough around electrical or fluid connections before cracking them.
- Buggering the mating surfaces of covers when separating them.
- Dropping ANYTHING into an oil gallery while it's apart.
- Not cleaning the mating surfaces well enough before applying new sealant. Proper degreasing is critical.
- Busting an electrical connector or bending a pin when reassembling.
- Over-tightening the most vulnerable 6 or 8 millimeter fasteners because "who uses a torque wrench on those?"
- Rushing or ignoring the evacuation step before charging the AC. This happens all... the... time.
The actual spring replacement, valve train clocking, etc... is not rocket science. What really bugs me is that book time is based on servicing a clean system. Most techs gloss over the details for the sake of expediency. I've personally seen and railed against it throughout my professional life.
Oh, and everybody fucks up from time to time. Rare and appreciated is the guy that isn't afraid to admit it.