Not right away. I'd want explanations for why they had never come forward before, explanations for why no one else had come forward. Other witnesses who would confirm their story or a good explanation of why such witnesses don't exist. I'd like an MRI to confirm they're describing events from memory. I'd like documents confirming the story. Some combination of these things could raise my probability estimation to belief-level. Frankly, it's such a complex conspiracy that a detailed account of how exactly it went down would put it on my radar.

Extraordinary claims require extraordinary evidence.

If they had it, yes. Not otherwise. This evidence would have to cover both the immediate claim (that they were working at NASA at that time) and the larger one (that the moon landing was faked). Evidence explaining why no one else ever came forward would be appreciated but not required if the other two things are present.