Separate 71/72 Inner Grill From Surround?

[Ironhorse]

Have been playing with these trucks for a good many years but never needed to do this? How does one separate the inner plastic eggcrate grill from the aluminum 71/72 outer surround successfully with no eggcrate damage? I have a really nice inner but the surround has a nasty tear about 6'' long at the lower section. Have looked and it seems the inner is held in place by plastic clips or inserts that are split similar to license plate plastic retainers. Also need to remove the two grill supports but since they are riveted will just drill them off.