Phone a local comic book store and ask if they do appraisals. Tell them it is for an estate.
Make an appointment. Keep the appointment.
Expect a written appraisal on letterhead. The value you get should be the value at public auction (as opposed to a cash offer to buy or an insurance/replacement value).
Expect to pay for the appraiser's expertise.
It shouldn't take long. The appraiser will want you to stay. This is for his protection ,not yours.
A free appraisal is worth every penny you pay for it.