The sentence 'Head off to the airport to ship out this stuff to Australia' is correct grammar.
The sentence 'Head off to meet with somebody to ship out this stuff to Australia' is not correct grammar because of the misplaced modifier.
"To ship out this stuff to Australia" is correct grammar.
'Head off to meet with somebody' is correct grammar, although the preposition 'with' can be omitted.
The sentence 'Head off to meet someone will ship out this stuff to Australia through plane' is not correct grammar because of misuse of 'will' and 'through'.
No, "will be had" is not a correct grammar. The correct grammar would be "will have."
No, here is the correct grammar: There are plateaus in Australia. Plateau is not a proper noun. In addition, you are using 'plateaus' as a plural of 'plateau'; the way you first wrote it indicates either possessive (the plateau owns something), or contraction (the plateau is something).
No, it is correct grammar, not a correct grammar.
The correct grammar is: "Are those correct?"
"On a train" is correct grammar.
No. "Somebody, call to me" is better.
The correct grammar for this sentence is: "When did you send it?"