1) You can use 'Copper Pour' to fill in Signal layers. change the Grid/copper width for continuous fill.
2) CAE is referred for Schematic symbols. Split/mixed referred for plane layer in which u can fill copper as well as route also.
3) first update the decal in library. Then in layout using ECO option u can replace the decal.
Click ECO--select the component--RMB Library browse--select the part-- update--then click ALL/selected.