SilentShot, I would strongly recommend that you go here first:
How To UseThis page explains the valuation pages for a litany of TSR products that are indexed on several pages. Please familiarize yourself with the Grading Conventions here:
GradingAll of the information you need to determine a rough idea of what each individual item is worth can be found on this site. If you feel that it would be too much work, then I would suggest you tell the forum members here where you live and if there is someone who lives in your vicinity, they might be willing to come over and give your father's collection an approximate appraisal and guide you on the best course of action to sell the collection. There have been multiple instances here in which someone has sold the entire lot to an individual who will then make the effort to re-sell each item. You have may options available to you.
Good Luck - Paul