Posted: 07/11/2014 at 12:59
I think you're right - drop the specific 'race pace' sessions, but look to include short periods of race pace running in your slower runs to get used to running at that speed.
Your four sessions a week seems sensible, with an interval, tempo and long run each week and the rest at easy pace. As its your first marathon, the focus should be building endurance, then Lactate Threshold and lastly any speed improvement.
For your long runs, it would be worth occasionally trying to run the last few miles at marathon race pace to get used to running that speed on tired legs. This is a good test and also a confidence booster (as it will be harder than you expect the first time, but will get 'easier').
If you have a look on the forum, you'll see a lot of references to the Pfitzinger & Douglas "Advanced Marathoning" book as it includes lots of useful details about the reasons behind the various training sessions that are included in most marathon plans. It might be worth picking up a copy even if you are devising your own plan rather than following one of theirs.