Attempted to put the minecart stage back into the final Wii game, with weird results.
Very basic stuff done, I'll post updates as I learn more about the formats.
0x04 to 0x0F = unknown, seems to be part of the header.
0x10 dword = number of files
0x14 dword = unknown
0x1C dword = address to the filenames
0x20 dword = address to beginning of the first file
0x24 dword = size of file
Followed by FF FF FF FF 00 00 00 00, then new file start address, and file size, check the dword at 0x10 for amount of files.
There is some stuff I'm missing in my format spec, but it works to extract most files.
G_ZONE*/MAP/ZONE*_ATTR.AMB is the collision data, and G_ZONE*/MAP/ZONE**_MAP.AMB is the level layout. There's a decent bit of research into the layout files, but that's not my work so you'll have to wait until the person working on that posts the info.