Former Jarhead here- so same training and a lifelong shooter. I went there in 2003 and did the same thing, after years of reading about what an impossibly technical shot it was that trained marksmen couldn't replicate, etc etc.
I was surprised that, once standing in the window (next to it, actually) it was a lot easier a shot that I'd been led to believe.
I wouldn't be at all surprised if there was a lot of funny business surrounding the events of that day, which I won't render an opinion on, but the shot wasn't as tough as it seems often made out to be, IMO.
That's right. Oswald had his rifle sighted in at a hundred, and was right on top of Kennedy as the limo turned onto Elm. the tree got in his way briefly, but after that, the shots were easy for a trained marksman. Oswald's kill zone really is tight, which the Zapruder film does not capture as the limo rounded the curve and then accelerated.