Ah, this all is a simple fix- and no worries about its size! Ye can change the size of the mesh when in the Map Maker.
To add on to what Kuri has said, to change the texture of the mesh, ye can also: find the right Material file. Open it with notepad and see what texture has been put there. From there, ye can change it to any image file ye want.
Hope this fixes y'er problem. If anything is confusing, I'd be happy to delve in a deeper explanation.