I suggest you visit the triathletes' forum. Lots of good training advice there.
Whether you can do it or not depends on you. But as Craig says, you have plenty of time to prepare. I trained for a Duathlon last year. In the end I didn't compete because I pulled a hamstring shortly beforehand, but I can tell you what I learned.
First, I learned to give myself time to prepare. I didn't really need to train for the cycling, I was easily fit enough for that, but I hadn't done any running for a long time, and I certainly hadn't done any running immediately after cycling. I didn't start doing brick sessions ( riding and running in the same training session) until much too close to the race, and that undoubtedly led to my injury as I tried to play catch- up.
So use the time you have. Start slow, running for just a few minutes at a time at first, riding on the next day, taking a couple of days off per week. Gradually increase the time spent in each session. Don't try to go fast at first, speed will come as you get fitter.
The surprise comes - came for me, anyway - when I started incorporating running and riding into a single session. Running then riding was no problem for me. But riding then running was amazingly difficult, my legs felt like jelly as I got off the bike and started to run. I asked an experienced triathlete about this and he said it is normal, there's no answer except practise. I had left too little time and as a result was transitioning from bike to run with tight hamstrings. Pop.
YMMV. I have no doubt that if you start training now you'll be fine, especially if you get some advice from people who know more about it than me.