How do I keep my body healthy while training for 26.2???

I trained last year to run a half marathon. I stayed injury free and very healthy! No black toe nails, blisters, sore shins, etc. I'm now training for a marathon and boy, my body is feeling it!
I ran in the rain one day (I know bad idea) and I had blister issues since then. Now, one of my toe nails is on the verge of kicking the bucket. UGH! I had such pretty toenails. I'm willing to pay the price though. I won't stop here and "quiting" is not an option for me. My knees and shins were screaming yesterday and my blistered/sad toe was throbbing.  How do you all stay healthily through this rough training? I'm lifting weights twice a week (upper one day and lower the one day). I'm doing yoga on my off day (mostly stretching and balance work), Zumba (one day a week) to add some fun in, and of course my running schedule. I'm trying to do everything to stay healthy and have a good balance. Any suggestions? Ice, Rest, and pain meds, anything else? Oh and I'm eating fairly well (balanced diet). Anything else?

I think that is's important to take it gradually and back off if you feel something comming on. I would advocate a 5 month training plan as opposed to a 4 for your first marathon because it gives a little make-up time for dealing with injuries. This is not for you but I would also recommend waiting a while and building a base before starting a marathon training. I think that people should spend a year getting their new eating habbits down and building that 3-5 mile base. At that point, I would recommend starting marathon training.

Anyway, I recommend, increasing mileage gradually and backing off if something does not feel right. If you start the race you will fini****'s better to go in under-trained than injured or over-trained.

 Having only done 1,  not sure I should give advice, but what Scott says sure sounds what I am thinking.  I was on the verge of injuries a lot, with the knees, calves/shins, feet assorted.  Not sure I ever had a week where I did all of what I was supposed to per the training plan.  I would just pull back a bit, take an extra day of rest. I also would use the TM more than running on the road as its a lot easier on the joints.

I did do some heavy cross training, and I did lift a lot, moving more to higher rep routine,

I think the main thing is to pull back and rest if you feel like you need it.  I did, and I still made it.  :)  

Make sure your shoes are large enough to accomodate the fact that feet may swell during running. I normally wear a 7.5, but my running shoes are 8W, whether it be Nike, Saucony or Karhu.

Also, since I live in the Pacific Northwest and rainy runs are practically a daily occurrence, I lube up my feet with Vaseline pre-run. I've never gotten blisters or black toenails in spite of running 5 days a week in all weathers, averaging about 60-65 miles a week.

If your knees and shins were screaming, my advice is to back off a little. Rest, ice, compression, elevation. Not too much downhill stuff--your knees will take a huge pounding! Plus, I use 5lb. ankle weights to do knee-strengthening exercises about 4 times a week. They really help!

As for the shins, shin splints are a red flag of "Too much, too soon." Rest--your body will thank you for listening to it and paying attention to its needs.