It sounds like you were in good shape, then missed a month due to surgery. You'll have to "cram" for you marathon. First thing-- double check with your doctor that it's OK to start running again and to do a marathon 2 months from now.
When you get your doctor's OK, I would suggest that you spend the first month of training gradually reconditioning your legs for running. After a full month off of running your connective tissue will be weak. Even if you feel like you are getting "back in shape" as far as running after a couple of weeks, your connective tissue will be lagging. So I would suggest being very patient for a month. Lots of short easy jogs to start off- start off with a 20-30 minute jog every other day. You can supplement by doing long hikes (at Valley Forge, perhaps), add a 15 pound pack to your back after hiking seems easy, also supplement with running in waist high water with your running shoes on if you have a situation like that available (try to use the same form and cadence as your normal running). You can gradually make your runs 45 minutes long as you feel strong, but make sure you go no faster than marathon pace (as a cap). If you have any problems with your knee, see your doctor.
During that month you will have rebuilt your strength and you'll be ready for 3 weeks of training followed by 1 week of taper. The name of the game is consistent moderate training. You'll find you should be improving constantly during this period, but don't give in to the temptation to "test" your fitness by going long or hard. If you try to run long or hard you'll probably fry yourself. I'd limit my long runs to 10 miles. The goal is to be coming into the race on the upswing and to be strong, healthy, a little undertrained and fresh.
This is how I would approach it. If you shortcut your early conditioning or try to squeeze in lots of training you'll be setting yourself up for injury and overreaching.