only to check that i'm understanding your post correctly:
I need the full Kernel-Sources for the Kernel-Version that's currently installed on my system ? Is that correct ?
What do i have to do with the Kernel-Headers and stuff that are actually on my hdd ? Overwrite them ? Erase them ? Make a new Directory to store them ?
No. The headers from the kernel that was on your VL iso are needed so that programs requiring glib can reference them.
And what means HTH some ? :-)
HTH some = Hope this helps some. :-)