I started running six weeks ago at about 190, pretty close to where you are!
There is a thread here on 3FC in the excercise section for people on the c25k (couch to 5K) program if you're interested in reading how other people are doing on it:
http://www.3fatchicks.com/forum/showthread.php?t=138627
You can also download music for the runs that tell you when to walk and when to run. I haven't used them, but I have seen that some people in this thread really like them.
Good luck!
Beth