Problems when editing road sign .wdr

[Hullian111]

When I was editing mh3_highwaysign18a.wdr to replace the textures with British-style ones, I've, no pun intended, hit a wall.

 

There are two problems I face right now:

1. If I try to import the .odr outside of the textures folder, the .odr replaces the .wdr correctly, but has no textures.
2. If I try to import the .odr within the textures folder, the .odr fails to replace the .wdr, showing the error, "Some files not imported, more information below. Fatal error: File "mh3_hwaysign18a_high.mesh" not found."

I believe that even when that is fixed, the textures will not show either. So is there a way to fix this, or is there a simple workaround for editing .wdr s?