bp - I did my first sprint tri this year on the back of little training but had been running and biking regularly and swimming was my problem area. did a few swims in advance and set myself a goal of 20 mins max for this which was about right as it was a very heavy swell in the sea. I would concentrate on your weaker events first but don't neglect the run if this is your strong event - it may help pull you up the field. I had a very good bike, and a below average run - probably too cautious
run.
best advice - go out and enjoy the experience, learn from it (it's very odd running after biking), and then decide if you want to do another and then work on a proper schedule.
btw - my total time was just under 1:30 - I would hope with proper training to aim for 1:15 to 1:20 this year.
good luck