It is kind of difficult to get models into Second Life.

SL does not support reading in a general polygon mesh object, instead it handles only prims that you create directly within SL, or a new "sculpt map" object.

You can get a 3dm2sculpt converter from here: http://wiki.secondlife.com/wiki/3dm2sculpt - that will enable converting from a .3dm file that MoI saves into a .tga sculpt map texture file (also check out the discussion tab there for additional details).

But the problem is that you can't convert just any object over, only "untrimmed" surfaces will convert into a sculpt map. So that basically means you can't use trimming or booleans on your object when you construct it in MoI, just build pieces only using stuff like Loft, Sweep, or Network.

Also the resolution of the sculpt map is fairly limited, when you convert it you will just get the sort of broad shape of your surface, small details and folds will not likely make it through.

- Michael