MPQ help

Hey everyone. I'm trying to make an altered melee map, similar to what TTOR has done. (Obviously with my own stuff though). I'm trying to make it so that the Corrupted ancient buildings replace the current ones. I remember I've done this before, but I cant remember how I did it If anyone could help me there would be a nice shiny new rep for you!

I'd assume open the MPQ in WinMPQ and change the paths so that the corrupted ancients overwrite the existing ones.

So I change the buildings\demon\corruptedtreeoflife\corruptedtreeoflife.mdx to buildings\nightelf\treeoflife\treeoflife.mdx... Ill try that. Thanks.