should I or shouldn't I?

short story: I am strugling with the decision to sign up for a marathon training group.

Good:
--(in theory) it will get me offa my butt
--I can say I ran a half and/or whole marathon!
--my health will improve. my dad evidently just had triple bypass surgery and was diagnosed with type 1 diabetes. he has been on high BP and cholesterol meds as long as I can remember. he has had TWO heart attacks, the first of which he was only about 35. surprisingly, while its been thought provoking, it hasnt given me the scare I think it should have. maybe it's because I really don't have a relationship with my dad?

not so good:
--it's kind of pricey. it's almost $200 for a years worth of support. when you crunch the numbers, its really not THAT bad (less than a gym membership) and you get other stuff too... but the immediate cost is high. at least to me, right now it is.

--what do I do if i back out? how do I keep myself from backing out? which I guess is my real fear. not running 13 or 26 miles, or logging all of those training miles. I am afraid I am going quit and waste all that money like i did with not one, but TWO gym memberships AND a boot camp, not to mention a master's degree.

--I don't really want to deal with matt poking fun at me about running a long race. he does it just to pester me, he would never doing something like that to be mean...but still. in my head, I know one of the best ways to be accountable is to tell everyone what I am doing that way they ask me about it. and I dont want to tell everyone that I bailed on my training...

these are just some of the thoughts going round in my little head...I kind of feel like im making a mountian out of what should be a mole hill, but running a half has been something that I have thought about doing for about the last year and a half. the major problem is that I lack the discipline to train alone and have found excuses to bail out of so many things, even things not related to my health and well being.

I have about two weeks to decide...help me.