Just finished my first tri. When I started swimming, I could do 50, maybe 100 yards before having to stop and rest. I would swim a lap and rest for 30 seconds, then do it again. I would do that for the whole workout. The next workout I would increase it by a lap. It didn't take long before I was able to do 9 laps, 450 yards, ~1/4 mile, at once. I was also on the swim team as a teenager. It'll come back. I swam the 500 yard leg in 9:43, which was faster than my pool times. Also make sure to do some open water swimming if the swim is an open water swim. It will really help. I didn't do that and wish that I would have.
I also read a bit about front quarter swimming. That was odd to start doing, but it helped out alot.
My sprint had a 17 mile bike, I didn't have aero bars, and neither did many others. Many people did, though.
I've heard doing the shoes clipped in bit helps alot on the time, but that it requires a good amount of practice. I didn't do it.
Then again, I didn't do it to win - just to finish!
EDIT: Oh boy - I just re-read and saw that yours was on this Saturday. So, slow down on your swim. Also, many people did the breast stroke or the sidestroke for the swim in mine. Don't worry if you have to do that. Also, to clarify: I did clip my shoes in on the bike leg, but I did not have them clipped in the pedals before I put my feet in them.