Find a different program.

The one you listed may get you to the finish line, but it will not likely be an enjoyable experience. If you feel you can run the 40+mpw and want to do a marathon (I agree with the 40+ wholeheartedly), just find another plan as there are many out there.

When I ran my first marathon my half time was 1:47, very close to yours. ( I ran that on about 20 miles a week)During my marathon, my training week average was around 28-32 miles. I topped out at 42 two weeks before the race. My long run made up a huge portion of my mileage. (probably too much) I would run 4-5 days a week running anywhere between 4-6 miles and then hit a big long run. I did a 12, 14, 16, 18, 20, 20, and a 21. I ran a 3:46 marathon without too much pain. Now...that being said, I would not train exactly like this again.
I would still run 5 days a week (I'm a bigger runner) but I would bump up my training runs to between 6-8 miles and then continue to hit the long runs. I also would run my training runs with more strategy (like taking recovery days!) I ran every training run pretty hard, including my long runs - which is probably why the marathon wasn't too bad considering my very low mileage. I also did no speed work, which was a huge mistake. Well, I guess that is how you learn. So, take it from me (a very inexperienced runner), run at least 40 miles a week, do some speed work, throw recovery runs in there, and you should have a good marathon.

Have you checked out Pfitzingers 55mpw plan?

I followed the same plan for my first marathon and finished in 4 1/2 hours, my goal was the same as yours, just to finish. I ran 4 days a week, whatever my long run was for the week i would do half of that run earlier in the week and then 2 shorter runs..something like this...4, 6, 4, 12. Each week it gradually increased up to a 20 mile long run. This plan worked great for me, I felt great when I finished and had no injuries while training. Best of luck to you!

for me pearsonally I was not concerned at all about speed work. I knew I wasnt going to break any records, I just wanted to finish and feel great the whole way so I didn't worry about speed workouts at all during my training.