You and I must be twins since I went through almost exactly the same thing- weight loss, limited funds, time and wanting to do some serious cross country.The second summer, after about a year of weight loss and some resonably serious training, I did a 600 mile group ride with woman tours with my sister- I rode a heavy hybrid and at the end of the two weeks I was wishing I had signed on for the enitre tour (meandering Missippii from NewOrleans to Lake Itasca MN along the Mississippi river)instead of just the first third.

The next summer I rode from Mobile AL to Niagara Falls on the Canadian side, also with woman tours, following one of the underground rail road routes.

Last summer I rode the Southern Tier from San Diego CA to At Augustine FL, again with woman tours.

The best training I did for myself was to develop a moderate pace of 15 mph that I could keep at for at least 6 hours, yes with brief breaks, but at least 6 hours TITS time (time in the saddle)- this usually worked out to almost a century, so I ended up the last few weeks before any long ride, devoting one day a week to a long 6 hour ride- the rest of the week I would do shorter,fasterr rides of 20 miiles or so.

It's more about consistency of training and getting comfortable with endurance type riding. On almost any long ride you do will have support in the form of a sag vehicle every 20-30 miles which will give you a chance to step down briefly- and that's a key word- and or an additional longer break for lunch. You will also undoutedly have the advantage of having a full day from butt crack of dawn until too dark to ride to cover whatever mileage the day requires and it will be a rare day that has so much mileage that you will feel pressured or pushed.

WT are my favorite tour company because of their experience, their tour guides and support vehicle drivers,their chefs/guides/mechanics and support (all female) on their cross country and long tours, and the all around excellent preparations, support, and conviviality of everyone who works with or for them. Most of all, the cameraderie that you develop riding with a group of like minded women in amazing. It's like mommy camp.

just my two cents worth.