Jennie, no, you've not bitten off more than you can chew. If you're up to 11 miles, you're already well into the distances that the training plans start - and you won't be doing that for at least another month yet! Keep on getting used to distances above 10 miles, and try to extend the mid week runs so that you've got that habit formed early.
I'll be turning 40 just prior to my 1st marathon next year, so if I can do it, so can you!
PB in a half today, under 2:20 (by 2 seconds, but under is under, regardless of margin). Which suggests I should be training for nearer 5 hours than 5.5. Golly, that's mighty quick (for me!)
Rachel, I ran for a number of years without a garmin, but decided that I'd get one this year. Had it a few months now and I love it! With a passion!! I'm completely the world's worst at judging pace, but this keeps me on track and gives me solid feedback on pace. And it goves it WHILE you're running, no waiting until the end and the clock to tell you that you were too fast or slow. There's something about the data that means you can't hide from it, and I like that almost brutal honesty from it. I went for the 205, as it does everything I need, but I'm completely in love with it. Used it today, and ran just the most excellently paced race (imho, obviously!) First negative split EVER, and finished like an express train! (I've had a glass or two of rather good red, so you might want to ratchet back the enthusiasm a bit)