Your plan looks much better now that you've removed the 24-26 mile long runs. Really no need for that. I'm not sure what your intervals and tempo runs consist of but you might find it hard to do two speed work sessions a week while increasing your mileage that much.
No more marathons
Robin - No big deal planning a marathon after little more than a year of running. Lots of people do it. And you've got a HM planned in there too.
As for the plan - plans get you started - you'll make lots of adjustments as you go along - having the plan gives you something to adjust.
One thing I'm missing - I don't see the 26 mile training run in the plan. With regards to that, if that's something you want to do, go for it - but don't expect that it is really going to help much in your training - in fact it will most likely detract because your recovery will be tough and it will set your training back a few weeks or more. Of course, with your longest run so far being 12 miles, that is also something that you may reconsider later on. Good luck, hope you can stick to your goal (and remember - the goal is to complete a marathon - not stick religiously to a plan). Adjust and adapt.
Boston 2014 - a 33 year journey
Lordy, I hope there are tapes.
He's a leaker!
If you were to remove one of the speed workouts, which would you remove? Are intervals better or tempo runs?
Why not alterante week to week? That way you can still do both but not try to do too much in a given week. I agree that trying to do 3 quality workouts (long run, interval, tempo) is too much. And you're increasing mileage. I might consider only doing speed work every other week, actually. You will start to feel worn down and not feel like doing speed work with the long runs and mileage increasing.
I wouldn't say one is "better" than the other... maybe others can offer a good explanation or different opinion?
Without knowing the details, I would say for a marathon, I'd keep the tempo run. Or alternate weeks like msmrow suggests.