Tom,
If you are holding 12-13 spl, speed ranging from 1:30-1:18 in Nov., with the goal of doing a 10 miler next summer, you will be more than ready to swim the distance.
A few suggestions that I have picked-up from friends that have done the Swim the Suck 10 miler(
http://www.swimthesuck10mile.com/Site/Home.html) Yes, that is a shameless plug for my friend's event.
1) Gradually build-up to longer swims by time, not distance. Start with a 10 minute swim, then work up to a 20 and even 30 minute swim. Don't worry about the distance, just get use to swimming relaxed for longer period.
2) Practice hydrating and feeding stops. You should be taking water every 25-30 minutes. Food is dependent on your body's need but at least a little energy replacement once an hour but water 2-3 times an hour.
3) Find a buddy(ies) to do some open water swimming. You may have to wait until the water temps warm-up in the spring(depending on where you are located) but get use to not having walls to turn or rest after 25 yds. Plus, you need to practice sighthing both in front of you and using the shore to follow for the swim.
4) Contact Coach Dave for specific training ideas. He has done a number of LONG open water swims. He will be able to give you even more details about what to expect and how to prepare.
Good Luck!
John