Marathon Training here I come!

It's almost summer, which means its almost Marathon Training time!!  The closer it comes to time the more nervous I get.  I've done 2 Half Mary's this spring and am planning on at least 2 more in the fall prior to the Full in November, but I still feel overwhelmed by the prospect of being on the course for close to 5 hours...  My "plan" consists of training to PR in August for my half, I want to finish in 2:15, I'm not a fast runner.  I feel like if I can do that I will be able to do the full.  

I've made out my training schedule and I think it made my apprehension worse!  From June 9 to November 2 (Marathon Day) I have 656+ miles projected!! That's a HUGE number!  I've laid out my plan and kept most weeks at 4 running days with Sundays as my long run, there are a few weeks that have 5 running days in them (mostly when there are shorter speed work days).  The original plan I was thinking of following had a long run of only 16 miles twice, this made me incredibly nervous, so I combined two plans and now have two different 20 mile long runs.  I haven't decided if that makes me feel better or worse.  Running a Full Marathon is no easy undertaking, if you've done it, you amaze me.  I'm not running until November and I'm already stressing about what kind of fuel I will need and where I will carry said fuel.  I'm stressed about the training and missing things with my family.  They are super supportive and want me to succeed.  It seems that once the longer runs start, the ones that go past the half-marathon mark, I will start to feel better about this endeavor.  

If you have advice feel free to leave it!!