My husband and I did a nine-day tour in upstate NY a couple of years ago (link if you are interested: Barry and Emily's Bike Tour). We averaged around 63 miles per day, which is more than you'll be doing on your tour, and we carried all our own luggage, which you probably won't be doing; that makes for slower and more difficult going. The best training tip I can give you is make sure you are doing several back-to-back rides on consecutive days. You need to toughen up your butt and legs to be able to cope with the day-in-day-out grind of a tour. Since we'd be riding for nine days straight, we did five consecutive days a couple of times while training to get used to that. It got pretty old to grind out those miles while training, but on the tour it was no problem with all the new scenery and sights to see. On weekends we'd do between 45 and 65 mile rides each day, and during the week, we'd do 25-35 milers after work. For the distances you'll be doing, you'll probly want to work up to 30-35 mile weekend rides (and yes, I mean both days) and 20-25 milers on a few weekdays. If you aren't able to do this fairly soon, you might not be ready for the tour this season.
You say you've been riding mostly on flat terrain. If the tour is on hilly or rolling terrain, you really need to ride on that type of terrain beforehand, and as much as possible. Riding on flats is a completely different experience than riding hills.
The other advice I'd give you is to resolve your bike issues ASAP. If you are getting a new bike, or trading out some component(s), you need to do this soon so that you will be training on the same equipment you'll be riding. Also figure out your clothing/gear needs; i.e., will you need to wash out shorts at night or do you need a clean pair for each day, do you have enough jerseys, socks, sports bras, and the like.
Good luck! Touring is very rewarding, but does take commitment and motivation. I hope you are able to do it - please keep us posted!
Emily
Emily
2011 Jamis Dakar XC "Toto" - Selle Italia Ldy Gel Flow
2007 Trek Pilot 5.0 WSD "Gloria" - Selle Italia Diva Gel Flow
2004 Bike Friday Petite Pocket Crusoe - Selle Italia Diva Gel Flow