Unless the code has been *really* well obfuscated,
and even if it has been, probably, there's many decompilers
available which can spit out source code for an assembly.
Yes. For example, Lutz Roeder's Reflector product, along with one of the
"generate files" add-ins, will allow you to decompile source code (including
a Visual Studio project file) from any assembly.
-Peter