You have to follow a few steps to get from the kernel source rpm to the full blown fedora kernel source code.
After you install the src.rpm, do this.
rpmbuild -bp --target $(arch) kernel-2.6.spec
After you do that, the source code files will be rooted at /usr/src/redhat/BUILD/kernel-2.6.15/linux-2.6.15.
To make the link you mentioned, you'll need to do this:
ln -s /usr/src/kerlnels/`uname -r`-$(arch) /usr/src/linux