WELCOME TO THE METRIC CENTURY CLUB! That distance is my preferred ride whether I do it by myself or with others. Once you feel comfortable about changing flats, you should be fine for riding on your own. I also carry a cell phone and go on routes where there are other cyclists around in case I get into trouble.

Actually, on the BJ there is a thread that deals specifically with metric centuries. It's a fun thread- even if you do more than a metric you only get to count it as ONE metric. This was to make it more equatable for riders who can't put in lots of time doing long long rides (double metrics, etc). Anyway, if you get a chance, I suggest you look around on that thread. Great stories about people's accomplishments which are truly inspiring!