How to Train For OW 10K

My club is putting on the 10K ow National Championships next summer. I like ow swimming and think I would like to try the 10K. I have completed several ow 5K's with no problem at all (I've enjoyed them) My best time is 1:27 and i'm 54 years old. I swim about 15,000 meters/yards per week. How much more would I need to swim to complete the 10K? What type of training should one do to get ready for a 10K The course is an easy double loop in a lake that tends to be non-wavy. Any advice would be appreciated. If you think it would be a bad idea for me to do it please say so. My biggest fear is shoulder injury and burn-out! :confused: