Replying to Anyone ever run a marathon/half marathon?

Hi all. I've been kicking around the idea (for the last hour or so) of training to run a half marathon. I've never done anything like this before, but it seems like a hell of a challenge. I'm not quite committed, but once I put it on my Bucket List, I have no choice. Anyone ever done something like this? Will I still be able to build a lot of muscle so I could play something like rugby, or are the two pretty much mutually exclusive?