About the source explanation, I was talking about any program in linux or even linux itself. For example, if you want to see the source code of xine, I think you can download the SRPM's for it, or just the source files (which are the tar.gz files). If you extract them, you should get the source.
About KDevelop, I never had any problems with it for simple C programs, but then again, I never really used it that much. Simply try to write some simple programs like the hello world example. You won't be able to write programs with windows API's of course, but there are a lot of libraries for linux which you can do the same with as in Windows.
Mandrake 8.2 should have it. Simply enter 'kdevelop' in a konsole to check it out. If it is not installed, you can probably install it from your Mandrake 8.2 cd's. Otherwise, you can download it from www.kdevelop.org.
About the tar.gz format. I don't know exactly what it stands for (I think 'tar' means tarball and 'gz' means gzipped), but tar.gz is actually exactly the same as .zip in Windows. To extract it, you can open it with Ark (simply double click on it), or you can extract it in the konsole with the following command:
tar -xzvf filename.tar.gz
(if the extension is tar.bz2, use tar -xvjf filename.tar.bz2)
Usually it will create a new directory in the one you're working in. Simply cd to the new directory to see the files.
I hope I was a help to you.
Good luck with it.