Ok you have 2 options currently.
You can use the .m3 import/export scripts for 3d studio max, found on sc2mapster.com or
You can do the following: (easier method):
Go to the actors tab:
Create a new action with the type "Site (Local Offset)".
Ok now you have offsets in 3d space, Z being up. You have to do trial and error (by placing a unit on the map then removing it).
Now go the the model or unit in question:
Make sure your viewing all the data you can alter on the unit/model's actor in a list form (but not raw data or xml).
Go to "Hosted Site Operations".
Add your "Site (Local Offset)" actor to this field.
Now what will happen is the model will be offset from where it normally is "center".
Now for the selection offset do the following:
Go to the models tab. Find the model for the planet you are looking for.
Now at this point I prefer to duplicate it and relink in the actors. Default stuff is handy to find references to in case you manage to play around enough with it to where you can't put it back to normal.
Now just go to the "selection offset" field and again offset in 3d space, Z being up.
Now a note: Just because the actor and its selection "appear" to be moved this does not mean that the unit is actually there. It is still in its origonal spot. So if you need to find its exact location via triggers and translate that to what it appears to be you will need to use the same offsets in triggers as well.