Stuart,
I have to agree with USMCRet93 whole heartedly!!!!! The only was to see Chuuk is via a liveaboard and there is only one.. TRUK ODYSSEY!!!! There are others on the island, but no comparison. You do not want to do a land based stay, because you are limited to the number of dives your can do per day. On the Odyssey you can do up to 5 dives a day. The Crew... they will spoil you, that is nothing to say about the meals and snacks you will get. The Odyssey is what I use to rate other liveaboards by.
It was March of the year I went and shorts and a tee-shirt were fine. As far as diving, I used a 3mm due to the fact of doing so many dives. I definitely recommend you dive with Nitrox. They offer it on board. I just reviewed my log book and I was showing a bottom temp of 82. The dive sites are spectacular and they explain each one to you prior to diving.
I envy you! I am so ready to go back!