Guam's "Pacific Daily News" has a nice overview of Guam that they publish, including a map of the island. The mission office is located on Route 8 in Barrigada.

PDN: Area Maps
PDN: Maila Halom, 2004

Questions about what to take to Micronesia are best directed to your mission president. I can recommend, though:

1. Take a good camera. There is so much beauty in the islands that you will want to keep and share with your friends and family. Digital processing may be available in Guam and Saipan, but probably not on other islands. You might have to send your media card home for processing, which could be risky.
2. You will want to represent yourself as a missionary, even on P-day. The more you can do to appear as a representative of the Lord at all times, the better off you will be.
3. Some of your companions and the families you work with will be from the islands, and will not have the kind of monetary advantage that an American would have. I would discourage taking those things that would distract you from your work, or that might cause undue envy from those who do not have such advantages. Many missionaries return home with nothing more than the clothes on their back, having given everything else they had to those who needed it more.