Due to the size of the collection ,It is highly unlikely you will want to send them to CGC, (a customer of mine just spent around 1,600 dollars on pre-screening .
Craigaigslist is fine but You will never get any true value off the lot.
I would suggest that you buy a price guide, it has all printed comics in it, the value by grades, as well as some notations.
it may take a week or so to get a decent valuation on the lot but at least you will be in the ball park on an asking price.
A comic shop may also offer to appraise them for a percentage of the sale or make a decent offer. I do this regularly at my shop.
Thisa is probably the cheapest and most profitable way to sell your dads issues.