" if early on he had realized that befriending the office staff would have scored him a permanent place"
I feel like you don't have any first hand experience with the kind of classist horseshit that is endemic to these kinds of work environments.
In my experience, it isn't necessarily classist horseshit that divides office and shop (or field) workers.
> They’d followed my oily bootprints down the hallway and begun to leer. Who is this diesel-stinking contractor?
That's probably the real reason. Being a welder is messy, stinky work and office workers don't want that in their space.
I do, thus my comment.
The key is to use this to your advantage.