How bad is it? It's among the very worst films; certainly the worst Bigfoot film!
Should you see it? Yes. But not sober.
In the early 1960's, a film was made titled something like "Teenagers vs. the Thing" but it never got released (because it was awful and too short). Later, a wrap-around was filmed, lengthening to 59 minutes, with credits, but making it somehow worse. The film starts with a guy lecturing high school students and reluctantly telling the story of his meeting with Bigfoot, which then goes to a 40 minute flashback. Kids investigating an Indian burial mound dig up what looks like the missing link, until it revives and starts attacking. It's not even Bigfoot, but a sort of mummy.