I see what you are trying to do, but neither os.walk or findAndReplaceWorkspacePaths works with wildcard syntax like '*'. First drop the * from os.walk, and drop the isfile call, since it's not needed. Then in each mxd you find, you'll have to iterate through the layers and tables, get the workspaces of the data sources, and replace one by one with replaceWorkspaces.
If it were me, I wouldn't change the path without spaces to one with spaces. That can cause trouble if you are not careful, both in scripts and toolbox tools. So I'd drop this entire project, unless there's a really, really good reason for doing it.
good luck,
Mike