Just curious, I'm not bashing on you or anything Hawklore, but ............
Is it his illness that sparks this interest in hearing his stories, or finding out he did something "exciting"? I mean, before when you thought he was a store clerk you werent trying to get stories out of him. Now you think he was a door gunner and you want to "know the truth". It's human nature to be more interested in exciting things than boring ones.
I think if I were you I'd express interest, then back off and let him make the decision to talk or not. I'll gladly give him a big for his service over there, but I dont think its right for you to use our well wishes to try to unlock that door for you. Either he wants to talk or he doesnt.
To this day all I know about my grandfather's service in WWII is that he fought in the Philippines, that he was with the 32nd Infantry, that he served in the Army of Occupation in Japan, that he thought the M1 Garand was the finest rifle ever made (and treasured his like it was made of gold), and that he killed at least one man hand to hand. I have a few stories, which were never completed because as soon as he realized what he was talking about he'd shut up. He was proud of his service, proud of the men he served with, but never proud of what he had to do. His brother in law was in Europe and fought at the Battle of the Bulge. Again, he didnt like to talk about it. They could talk to each other, and did, but they couldnt talk to the rest of the family and we never pushed. My uncle was in Vietnam. Same story.
What it boils down to is, some things are just too painful to share. It requires a special bond to talk about those things. As close as I was to my grandfather, it wasnt enough. I respected that, and you should respect your Uncle's choice.