What is the significance of Winston's Job?In the Story? To the Party? To Winston? If His job exisited in the real world?

Winston's job at the Ministry of Truth serves as a form of satire and irony.  We don't expect a censor, an agent of propaganda, to be a rebel.  His role in the party is to retroactively cover up the way the Party vaporizes people.  It is ironic that this will eventually happen to Winston; he will become an unperson, like Oglivy, the man whose records he sends to the ash heap of history.

Through Winston's job, Orwell give us access to the Ministry of Truth in Part I of the novel; later, he will give us access to the Ministry of Love in Part II.  Orwell's primary focus in the novel is on the death of language (Part I) and the death of the individual (Part II).  Winston sees both firsthand.

Censors exist in nearly every profession: schools, offices, government agencies, churches, entertainment industry, and especially the online world.  They may have a doublespeak title, like "editor."  For example, the MPAA hires a group to attach film ratings to motion pictures.  If the film is too sexually explicit or violent, the movie will be sent to the cutting room (like the Ministry of Truth) to have the racy parts cut.