As long as you will be gone less than 6 months, you don't need a re-entry permit (I know USCIS says "1 yr", but I always recommend it for 6+ mos).
As far as your CR goes, you should not have any problem re-entering the U.S. prior to the expiration of your card. I would recommend that you file the I-751 closer to the 90 days prior to the expiration of your CR anyway.
As long as you will be gone less than 6 months, you don't need a re-entry permit (I know USCIS says "1 yr", but I always recommend it for 6+ mos).
As far as your CR goes, you should not have any problem re-entering the U.S. prior to the expiration of your card. I would recommend that you file the I-751 closer to the 90 days prior to the expiration of your CR anyway.
