Who can write?

I've been thinking a lot about writing a book, and I have a few good ideas, but I think it would be better to get a graduate degree, before I try to publish, for credibility purposes. Does anybody know anything about the process of getting a book published? Also how many "pages" on MS word would be equivalent to a 250-300 page book? What do you guys think? As Sheldon put it, "Pleased to meet you Dr. Gablehoueser, how fortunate for you that the university has chosen to hire you despite the fact that you have done no original research in 25 years, and instead have written a series of popular books that have reduced the great concepts of science to a series of anecdotes each one dumbed down to accommodate the duration of the average bowel movement. Ma-halo"