You can get MAX objects out of MAXScript wrapper values in several ways:
virtual INode* to_node();
virtual Mtl* to_mtl();
virtual Texmap* to_texmap();
virtual Modifier* to_modifier();
virtual Control* to_controller();
For example,
INode* node = arg_list[0]->to_node();
virtual ReferenceTarget* get_max_object();
Note that this function will retrieve the base object in a node inside a MAXNode wrapper value, rather than the INode itself. The reason for this is explained in the MAX ClassIDs and SuperclassIDs topic.
ref = arg_list[1]->GetReference(0);