I'm assuming you mean planar UV maps.

No matter how many you have, they all should be 1 UV map. If you have one of them selected, only it will show up in the UV Editor, but if you just select the model, all of them will show up for editing.

As for exporting to max, just make sure the UVs are layed out and export as an obj. Max does have an obj import plugin, or you can use a program talked about in the recent export thread to convert the .obj to a .3ds file. In max, it won't have the textures applied, but it will have the UVs and it's a fairly simple matter to apply the textures again.

Note that maya materials and material effects and settings are not compatible with Max's, so if you have a special material that you've set up, the only thing i know to do is to remake it in Max. There is no way to convert it over, as far as I know.