What is the ruling on the Hajj of one who is unable to wear the Ihram garments due to the nature of his work, and is his Hajj valid with a Fidyah (expiation)?

Your Hajj is valid, and there is no sin upon you for wearing clothes other than the Ihram garments to avoid embarrassment. However, a fidyah (expiation) is required for this, which is to feed six needy people from among the poor of the Haram, or to sacrifice an animal suitable for an udhiyah (sacrificial animal) and feed it to the poor of Mecca or elsewhere in the Haram, without eating from it yourself, or to fast for three days. Whichever of these you do will suffice you. And the same applies if you covered your head.