... Max Skinning (how i do it) generally goes like this ...
select the surface i want to skin, UVW Map Modifier and set a basic map, then Unwrap UVW Modifier to edit it into fit in the map right.
try to make sure the major sections of the model line up, and no you can't have multiple UV Maps per object only per model - if you need to use another map select the faces you need as a seperate map and detach them as a seperate object.
this is a limitation in the Dx/3DS/MD3/MD2/MDL formats
if you need to create decal maps, then you'll have to do this either as part of a seperate map and use the "detail mapping" function or just combine with the texture itself. eitherway you'll get the same result.