Go to the following USCIS processing times link, and scroll down to "National Benefits Center": https://egov.uscis.gov/cris/processTimesDisplayInit.do. The NBC's 8/31/2013 processing times are available, and you will see that as of 8/31/2013, they are processing applications received on 10/1/2013, so it would be approx 10-11 months.
Long time, a lot of effort and expense, much of cooperation from you and patience and no guarantee of success.
The information contained in this answer is provided for informational purposes only, and should not be construed as legal advice on any subject matter,not should it be viewed as establishing an attorney client relationship of any kind.
Probably 6 months to 1 year.
Angelique Montes, Esq., Immigration Attorney in Houston, Texas. This is not legal advice and a client-attorney relationship is not created. The above is intended only as general information, and does not constitute legal advice. You must speak with an attorney to discuss your individual case.