I got my books last February and implemented WW then. I did not start with Launching WW. I started with Small Moments and skipped a lot because my kids were past it. I would say to start it just so you get your feet wet and then the following year implement it fully.
Like the PP, I think you can use a great deal of the Units of Study for Writing. You probably won't need much of the Launching unit because you probably have taught those skills already. If there are a few parts--teach those. Then you can move on to Small Moments.
I think all of us (as first grade teachers) probably pick and choose which lessons we are going to use. Some may be unnecessary--and lack of time to teach the entire Units of Study.
They are so wonderful that I wouldn't miss out just because it's November!
It is not too late to start WW. However, I would suggest you read the Launching Unit/Nuts and Bolts to see the management part of it. To me that is one of the essential elements for WW success. You may already have something in place, but it was a definite eye opener for my colleagues and me because it went into minute detail on how to get the students working independently, from what supplies you need to how they are distributed, how to group students, how to conference, etc.
I agree with the other posters. You can definitely start with the units now, it is not too late. Of course you will have to pick and choose which units you will teach this year since you won't have time for them all since you're starting late. I highly recommend the small moments units-my student's personal narratives have really improved as a result of this unit. Good luck!