Would I be adding my option to the end of that line or does the first line default to latest installed kernel?
Unless you have manually edited menu.lst, the default "title linux" boot menu section will always load the kernel which was last installed. Just to be sure of which kernel version vmlinuz points to, do a quick check in a terminal.
[darrel@Duron ~]$ ls -l /boot/vmlinuz
lrwxrwxrwx 1 root root 27 Jul 26 20:55 /boot/vmlinuz -> vmlinuz-188.8.131.52-pclos3.bfs
Would it hurt to add the line to each of the booting perameters?
I should have said "Find the line(s)
beginning with 'kernel' ". I should also have added that the pcie_aspm=force
parameter should only be added to a kernel stanza that loads one of the kernels with the power management regression. If the kernel to be loaded has the power management regression, by all means, add the boot parameter.