Does anybody know the name, the details of this mission, or if it even exists?

Mission 6: Undeniable Assets comes with the Lambda Shuttle. It involves the Empire trying to rescue passengers from some disabled ships. What exactly did you want to know?

A link please, and is mission 7 coming with Imperial Aces?

It comes on the rules pamphlet in the package with the ship. To my knowledge, none of those (from the Falcon, Slave I or the Shuttle) have been released as pdfs or are available online.

As to Mission 7, your guess is as good as mine, but it seems like a likely possibility.

If I recall correctly, mission 7 will be in the Imperial Aces pack and will involve the Empire protecting a prototype fighter. I believe it is called Cutting the Cord.