1) I'll jump on the bandwagon that's already rolling. As long as you let us know of changes it's fine to post new chapters as you revise.
2) Good settings help a story immeasurably. It's just a question of what sort of story you want to write. Lot's of discursive description might bore people looking for an 'action/adventure' story. But this looks like a whodunnit, and we all know that whodunnit's hinge off details.
If some point of the setting/background is necessary to the story, you'd better describe it in detail.

It's probably most effective to deal with the pertinent details from the point of view of whichever character is a stranger to them, so we have an excuse for a 'newbie' level explanation.
3) Excellent idea, for the reason cited above. You get to describe things from the point of view of someone unfamiliar with them and it gives a good excuse to fill the reader in. Also, switching points of view back and forth could let you pull some tricks, if you're clever. As already noted, 'whodunnit' mysteries hinge of small details. You
might use the device of describing things from odd viewpoints to conceal major points in the story until the Last minute. It might take some time for those two 'aliens' to fully understand eacch other, and while they are not fully certain of each others meanings all sorts of things can pass through the net.
Don't over do the violence unless you're really aiming for an action/adventure story. I don't think the genre's mix very well.
And surely by now you realize that every single person in this forum LOVES to speculate on SciFi technology, gadgetry, and alien life. You've got a whole committe of anxious and eager collaborators waiting if you would like to toss some problems out for us. Then stand back!
[ June 05, 2002, 05:07: Message edited by: Baron Munchausen ]