I've never been asked to handle that directly but was tasked by a church brother who had reluctantly got stuck being his golf buddy's executor. Luckily I did not know the deceased. I hauled tools to my friend's house, where he had the entire "collection" laid out and a spreadsheet started, with a printout for me to pencil in data. I cleaned, inspected, graded, repaired where necessary, and priced from the current blue book. It took me four days. When he asked what he owed me, I said, "whatever you think it's worth". He told me to pick any gun (an unfortunately bumper-chromed Deerstalker) and then told me to pick another (a pristine 5" M27) and because my friend was the cutout between the heirs and myself, I had no qualms about accepting them. The Deerstalker gets warmed up regularly and the 27, after a bit of shooting, the installation of a target rear sight and a bit of duty carry, is my only safe queen but will go to my eldest.
As for my own guns and loading/casting gear, I maintain a spreadsheet including the intended recipient and that will be appended to my will.
Ed <><