It's risky and often counterproductive to look for unseen second
guesses, expert or otherwise, when you are not doing the work yourself
& a shop is about to assess it firsthand. Unless they are grossly
incompetent, the best you may do with other input is to prejudice their
thinking & delay them in locating the real problem, or maybe **** them
off. If you don't trust them you shouldn't call them aboard. BTW a
disassembled & cleaned head is easily & inexpensively inspected for
cracks or similar flaws by penetrant dye-checking, requiring no x-ray.