The written might be a bit different now, but when I took it circa 2003, it was essentially the same as the ATP written. I decided to take the dispatcher written test and get my certificate just as something to stick in my back pocket, and to refresh some of the material as at that time, I already had my ATP written and was getting close to taking the ATP checkride (did it in a Semi-slow). Lo and behold, my first 121 job was as a dispatcher at a regional airline. Real soon after that, the calls to interview to fly started coming in. (During the tech interview at one regional airline, the interviewer skipped about half the questions saying I'd know the answer since I was dispatching, just his assumption.)

Most dispatcher programs are about three months long for the person who wouldn't know an airplane if it hit him in the butt. The school I went to, and most others, I believe, have a short program if you have proven aeronautical skills - a private pilot certificate will do. In that case, it's some home study and tests and a one-week program to hit the advanced material followed by the "checkride" (oral and flight planning, old-school style).

Getting your dispatcher certificate isn't going to be difficult. Getting hired at a major without prior DX experience might be, but having the TPIC time may help. Best of luck to you!