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I recommend starting with this tutorial.
http://www.vogella.de/articles/AndroidLocationAPI/article.html
That will get your feet wet in loading up maps.
Then use this tutorial at the bottom it will reference itemized overlay which will enable you to add all the weapons and respond to events when you click on it.
http://developer.android.com/resources/tutorials/views/hello-mapview.html
Your game sounds fun!!!
You can check cloudmade's specialist tools
Also there is static maps api from cloudmade
U can check a list of apps/games made using this here