I note your statements that you have a large number of guns to go through, that you do not wish to keep many of them, that you wish to maximize the proceeds for your mother-in-law, and that you are a novice. With all that in mind, here is my 2 cents worth:
Do not set a price for your M1 Carbine, or any of those other guns, based upon the Blue Book, or some website, or anything you read on here. Get a serious appraisal in writing done by someone who knows guns and can examine yours, and then go from there. You also might want to consider consigning them at a dealer, rather than trying to sell them yourself. Here's why:
There are many subtleties and nuances in gun collecting, especially with old military arms. The value of your Carbine could be significantly affected by such things as condition, originality, maker, serial number, etc. Handgun values can also vary widely depending upon the number made, condition, whether the original box and papers are still with it, etc. Sharks who know this take advantage of novices like you all the time.
About 10 years ago a friend of mine died unexpectedly in his sleep. He had a rather large collection of relatively rare firearms. His grieving widow thought it would be too much trouble to have those guns appraised and/or consigned, so she let her sister's boyfriend bring his Blue Book over. After looking up the guns in the BB, the boyfriend offered to "take them off her hands" for a song, and she, not knowing any better, sold them to him.
You are in almost exactly the same position that young widow was in. Don't let yourself get taken advantage of like she was.
Please accept my condolences on your loss, and good luck to you.
