Off Season training for first triathlon

It sounds as if you are just coming off another training plan and are looking to customize to meet your needs.  There are sevetral winter maintenance training plans available here so I'd suggest to check those out if you haven't already.  Outside of that I'd say that any training is better than none.  Even if you just alternate discipline workouts each day and do long workouts on weekends.  That's the approach that I'm taking right now.  I just do bike one day, swim the next and run the next (rinse and repeat) for however long I have to dedicate each day.  We are all busy people and so don't feel like you have to get locked into specific goals each week and if you don't meet them you've failed.  That's what I used to do and I got discouraged.

June 2011 is a long ways away.  Right now just concentrate on getting/keeping a base of fitness and then next spring really concentrate on keeping to a plan to get you to peak at race day.  Calculate 8/12/16/20 weeks out from race day and mark it on your calendar to start a formal training plan then.  Until then, just have fun keeping in shape.  Working out should be fun or why do it at all??

Hope this helps. 

As you said that you don't have much experience in the pool I don't think once a week is going to be enough.  I'd try and get in the pool at least twice a week, especially if you are planning to do an Oly.  It can be easy for now and then ramp up in the Spring as has already been suggested.  Good luck!