Couple of things to keep in mind about time. First of all, you have to run a 10K after your 40K bike. So where as in a TT you want to be completely spent by the end or you didn't go out hard enough, in a tri you need the energy to perform well on the run. In fact, you usually loose more time by going too hard on the bike and not having enough for the run than holding back a bit on the bike so you can go faster on the run. This is more and more true the longer the distance of the race. Avoid trying to win the race on your bike. This is important since you are coming from a cycling background. Do a solid bike split, but save plenty for the run. I'd do plenty of bricks (workouts with both bike and run training) at LT before your race so you can get a feel for running off the bike.

Second thing is your transition times are included in your total time. This is the time from when you get out of the water to mounting your bike (T1) and the time from your bike dismount to getting onto the run course (T2). Depending on the course and transition area layout, this adds anywhere from 3-10 minutes to your time. As a newbie, you'll likely be on the longer end of this. Keep that in mind when thinking about your time goals. Pros and many dedicated ager groups spend time leading up to races practicing transitions so they are done as quickly and efficiently as possible. It really is free time, so if you can do quick transitions, it's a real plus.