I'm surprised ( an not pleasantly ..) to read that these gaskets replacement interval is suggested at 40 k miles, not to mention Sean's car which needed it even earlier than that . Not a single car I have owned , and we're talking about at least 25 + in the last 40 years or so, has ever had a valve cover gasket fail earlier than 100 K miles. And although many of my cars have been Porsches and Mercedeses, I've had quite a few inexpensive cars also, where you'd expect the quality of the parts is substandard as well..and no gasket leaks there either . Ugh, rather disappointing to hear this about our cars .
As for the job, most definitely check with independent shops, this is not any kind of work which requires specialized or unique dealer equipment and so called expertise for which you have to pay an arm and a leg .. I checked out a highly reputable local exotic car independent repair shop ; Ferrari , Maserati , Aston Martin, MCLaren , etc.. and asked them about charges for various service and repair jobs for the Maserati GT . In almost all cases the labor time was just about half of what the dealer indicated for the same job.