Compiler and header question

I have a consultant working on getting Authorize.NET working on my Debian
woody machine, he is having a problem compiling software required by
Authorize.NET.


>Looks like an environment issue. Do you have a C compiler installed?
>If not, you probably don't have the header files (usually located in
>/usr/include). Verify that you have a C compiler, and the headers are
>indeed in /usr/include.

when I do a "dpkg -l gcc" I see the following.

"ii gcc 2.95.4-14 The GNU C compiler."

Ok, so the compiler is there...

How would I verify that the headers are there?

And if they are not there...how do I get them to /usr/include?

Thanks,

-Milea