Mountain Mitch

I'd suggest keeping the bike as is and carry absolutely minimal stuff - like maybe a handlebar bag worth of rain gear and bars. Then do a 'credit card' tour on Hadrians Bikeway. Should only take a few days and there are lots of places to eat and sleep on the way. This's will allow you to feel a sense of accomplishment and let you know if you like touring and if you and the bike are up to it. If you are keen afterwards you'll have a much better sense of what will work for you in the future. And don't worry about your weight. Ride lots and eat smart and you'll be surprised at how easily the pounds slip away. Check out the Clydsdale posts.