Factually Based?

No. The film is complete and total BS.

I'll Teach You To Laugh At Something's That's Funny
Homer Simpson

There is a lot of anecdotal evidence that Patton was assassinated, not killed as the result of an accident. Included in the evidence is testimony of those who were involved, or aware of, the plot. Google Douglas Bazata and the book, Target Patton. Bazata stated, before the movie was filmed, that he was involved and had
ordered and used the weapon which shot various objects.

I believe there is still controversy as to how Patton was actually killed (aside from the obvious accident). Whether or not one plausible interpretation of what may have happened is depicted in this film, it was still entertaining, even on the fictional level. I'm not sure if the stolen/missing gold aspect of the plot is fictional, or not.

A good read about the gold: http://www.archives.gov/publications/prologue/1999/spring/nazi-gold-merkers-mine-treasure.html