Whether we have dropped a load of debris into the cylinders? Have we purchased the correct gasket? Do we possess a suitable torque wrench and know the stud tightening procedure and sequence?

Hopefully the mechanic torqued the nuts and replaced them in the correct pattern. Also, you'd want to make sure all the necessary vacuum lines and sensors were hooked back up properly.

Are you confident that the person(s) doing the work knew what the correct procedures are and that they were followed?

If so, hopefully you won't have anything to worry about.

find local shop at ATRA.COM for free road test to determine if it is slipping

not sure what your asking here? way would you be worry about anything.

your mechanics ability

Paying the bill !!!!!