Q:

"gonna/going to have to" vs "have to"

Is there a difference between "gonna have to" and just "have to"? For instance, in the following two sentences:

You’re gonna have to be completely honest.

and

You have to be completely honest.

A:

"Ya gonna hafta" is a sort of African American Vernacular English--but even so, it's not the kind of thing anyone would usually say.  You'll only find that in song lyrics...or when someone is really trying to be over-the-top in a "telling you from the soul" way.  They want to let you know the hard truth about some tough thing you must do--for reasons of moral obligation or fundamental necessity.
Basically, avoid using "gonna have to" unless you have a grasp of the subtleties; it's slang.

You have to be completely let me.

That makes no sense.  On the other hand, these sentences make sense:

You have to be completely honest.
You have to let me take care of it.
You have to completely let go.
You have to be completely calm.
You have to be completely willing to let me take care of it.

When you say someone "has to be X", then X must be a "state of being".  "let me" is not a state of being.  "willing to let me take care of it" is.

