Scrum Planning Question from Scrum Open Assessment

Should the Sprint Backlog be complete and detailed in Sprint Planning?

The Development Team invites external people to the Sprint Planning to ask them how to turn a Product Backlog item into an Increment via a complete and detailed Sprint Backlog.

The keyword here is "HOW". There is a difference between asking others for advice from a technical or domain point of view versus asking others how to do the work. 

From the SG:

• "Self-organizing teams choose how best to accomplish their work, rather than being directed by others outside the team." (The Scrum Team, Pg 6)
• "They are self-organizing. No one (not even the Scrum Master) tells the Development Team how to turn Product Backlog into Increments of potentially releasable functionality" (The Development Team, Pg 7)
• "the Development Team decides how it will build this functionality into a “Done” product Increment during the Sprint." (Sprint Planning Topic 2, Pg 11)

Isn't asking them how to turn a Product Backlog item into an Increment via a complete and detailed Sprint Backlog some sort or technical or domain advice?

Asking for advice from a technical aspect is not asking how to finish something. The team can ask the architect for advice to ensure they are pointing to the correct endpoints or database or ensuring the work is consistent with the organization but they still determine how they would accomplish that. 

Hope this helps.