The term was in existence for centuries before Said converted its meaning. The orientalist was someone who studied or held deep fascination (say a collector) for things oriental, orientalism was the project and product of that study and collection. Said re-cast the label into one for an ideology.

We can go to Said's words themselves for confirmation, from his introduction:

It will be clear to the reader [...] that by Orientalism I mean several things, all of them, in my opinion, interdependent. The most readily accepted designation for Orientalism is an academic one, and indeed the label still serves in a number of academic institutions. Anyone who teaches, writes about, or researches the Orient—and this applies whether the person is an anthropologist, sociologist, historian, or philologist—either in its specific or its general aspects, is an Orientalist, and what he or she does is Orientalism. Compared with Oriental studies or area studies, it is true that the term Orientalism is less preferred by specialists today, both because it is too vague and general and because it connotes the high-handed executive attitude of nineteenth-century and early- twentieth-century European colonialism. Nevertheless books are written and congresses held with "the Orient" as their main focus, with the Orientalist in his new or old guise as their main authority. The point is that even if it does not survive as it once did, Orientalism lives on academically through its doctrines and theses about the Orient and the Oriental.

Ooh! One I can answer.

Yes and no.

He did not coin the term, per se. It had been used previously in art history. However, he "forever redefined" it. (See Tromans, The Lure of the East, British Orientalist Painting.)

Essentially, he co-opted the word from a different field (in which it didn't have much emotional valence) and applied the connotation to it that we currently assign to it--thus making it, to some degree, a new word.