I did a quick scan, but didn't see anyone mention these specific points. If I repeat someone else, well, just call it a 2nd opinion...
1) IF you feel comfortable, put your housing on a lanyard around your wrist. I saw some mention of taking it in and out of a BC pocket. Not only will the housing be too large for most pockets, it will also be VERY positively bouyant. Once out if your grasp, it's gone. Keep the lanyard short - if you do happen to let go because you need your hand, you don't want it getting tangled.
2) Digital cameras generate heat. Tahiti has lots of humidity. Take along silica packages (or desecants designed for your housing) to place inside the housing to prevent lens fog. If not, after 30 mins in the water your camera will only take pictures of clouds...
3) Skip the external strobe for now. Yes, this will cut down on the types of pictures you can take, and the quality. But let's face it - this is for the memories, not the gallery...
BTW - since you will probably be doing more than 1 dive, talk to your dive operator and tell them your situation - you're fairly new but would like to take pics. Don't take the camera on your first dive, but by all means, when you have a shallow reef dive without current, I see no reason to leave the camera topside. Your operator should be able to tell you a good dive to try it out on.
Have fun!
