Are you looking to Just Finish the Race? Or kick some trash? (I hope it's the second option...even though around mile 18 or 20 my point of view always changes...)
There are so many ways to train for a marathon, or any race, that things can get confusing. I've trained for marathons with lots of milage up front and speed work at the end, and the opposite way with speed work first and mileage later.
I am personally a fan of doing speed work first. This training method makes sense to me...and, if you haven't noticed, I like speed work. There's a LINK to the training program that I've used with the speed work up front.
I would suggest that you do find a program that fits your goals and abilities. Having a program is motivating, safe(r), helpful, and confidence building.
I would also suggest that you do get a LOB (Lot Of Both--speed work and milage---I just can't stop myself). Mileage is important, but so is having a fine tuned engine.