[R] easiest way to extend and recompile a package?

[Michael]

Hi all,

I am thinking of extending a package by directly adding stuff to its
C++ code. And then I have to recompile the package.

Do I have to download the whole R source repository, in order to do
the recompilation? What is the minimal setup requirement for such a
recompilation?

I am using MSVC Express 2008 on Windows, is that okay?

Please give me some guidance. Thank you!