Training Plan for First Trail Marathon

Hello Ultra peeps!

I'm planning on running my first marathon this December. I'm not ultra material quite yet, but I thought I would ask this question here since the marathon happens to be a very hilly trail marathon, the North Face Endurance Challenge here in San Francisco.

I won't start training until after my HIM in July, but being Type A I'm already looking at my options in terms of a training plan to prepare for the race. Based on a February half marathon I'd be looking at a 4:45 - 5:00 finish for a traditional road marathon, and I know a trail marathon will take me considerably longer. I'm planning on doing most of my training on the trails where the race will be held.

Do you have any recommendations for training plans that would prepare me for a hilly trail marathon? Should I just take a traditional mary plan (I used Higdon for my HM) and do most of my training on hills and trails? I wasn't sure if there are any plans out there that are tailored more towards trail running.

Thanks in advance!