Welcome to Wellesnet, Sinatra70!
I'll start off:
What may throw you, at first, is "the newsreel" about DeHory he slips in at the beginning, but in my opinion, F FOR FAKE is Welles' second best film. Others may talk about THE MAGNIFICENT AMBERSONS, CHIMES AT MIDNIGHT, OTHELLO, THE TRIAL, TOUCH OF EVIL, MR. ARKADIN, etc, but good as they may be, there always must be a caveat:
If RKO hadn't hacked 20 minutes out of it; if the sound track could be fixed; if the original version had been restored; if the ending hadn't been changed; if Murch hadn't been quite so faithful to the memo; if that London copy could have been found; and so on.
F FOR FAKE is the film Welles wanted to make. It is his creation, and neither he nor anyone else need make excuses for it. The film, as you suggest, is a new departure for him, his first in color; a film essay suitable the 1970's and the medium of Television.
Not only that, but F FOR FAKE is Welles' testament, as close to obvert autobiography on film as he got. It recapitulates all his former interests, and introduces a consuming interest of his later life: Oja Kodar.
The film resembles a CITIZEN KANE with the Director/Magician coming out from behind the green curtain. That first hour you found hard going -- "the truth" -- shows us all his interests: Art, Magic, Story Telling, Europe, America, History, Beautiful Women, Eating, Drinking, Old and Powerful Men, Intrigue, Mystery, Artifice, Editing. And the last 17 minutes that you like shows the gorgeous sausage, the observations on the nature of Art that he makes out of his materials. He ends with that sublime meditation upon what Reporter Jerry Thompson said about Charles Foster Kane, what Tanya said about Hank Quinlan.
As in the case of CITIZEN KANE, and a number of other Welles' films, I see something new in F FOR FAKE every time I watch it.
I hope that you will, too.