The true value in your dad's stamp collection lies in the fact they were your father's collection more than their commercial value today. Think about keeping them so you and future generations of your family have this keepsake.
Collecting for the enjoyment of collecting, whatever that might be, is the name of the game. Don't hesitate to ask questions especially if you need basic information and especially more advanced sources of information for any possible topic. You should be able to find folks on this board a little further along on their collecting journey glad to share experiences.
My personal bias is a used stamp loses the story of its journey in the postal service when it is removed from the cover it transported to its destination. Collecting postal history adds a whole new aspect to your journey in our hobby.
Wishing you many enjoyable future days in our hobby. Russ