Easiest way I've found to do that sort of thing is to use ILDasm to extract all the IL into a file and extract all the resources. Just take the resource you want to edit, edit it, put it back in the same folder you extracted all the il to and then use ILAsm to put it back together.
A simple example of the round tripping of a .net assembly (what the process I described above is called) can be found here: http://jasonhaley.com/blog/post/2004/06 ... t-exe.aspx
though it doesn't cover taking the resources file and converting it to an resx file so you can edit it in VS.
You can use ther Resgen.exe tool to convert the resources file to an resx file - and vice versa. http://msdn.microsoft.com/en-us/library/ccec7sz1(VS.71