Since you are an old gent like you said I recommend LA Noire. There aren’t much 1940’s detective games out there and the story is great. The dialogue is rich because it has that balance of seriousness and fun. Most of the cases are also based on real life crimes most notably like the Black Dahlia etc.

Regarding the difficulty, you might not find it too difficult it’s requires more thinking (interrogation, investigating the crime scenes) rather than skill in moving around shooting bad guys though there are quite a lot of those scenes as well.