I don't know how much has changed between 2008 and 2014, but I recently installed Ubuntu on a 2008 MacBook Pro and it was amazingly simple. Since Mac uses EFI boot, the machine I was working with detected my Ubuntu 15.10 drive without issue using the stock bootloader (though I had to add "nomodeset" to the Grub boot command or Ubuntu would hang.) Simply make free space on your disk using Mac's a boot disk utility (or not if OSX won't even boot,) make an Ubuntu live USB and plug it in, hold the Option key while it boots, and select your drive. Once booted, install like normal.
I did a dual boot, but if you indeed plan on completely replacing OSX, this post has instructions for rebuilding an EFI boot partition: EFI boot Ubuntu 14.04 on a Mac without rEFInd
If the current OSX installation runs at all (or can be fixed using recovery (command+R at boot)), it may be wise to make an OSX install disk just in case running Ubuntu turns out to be more of a fight than you want to deal with (which was my case): http://macmint.com/how-to-make-an-os-x-yosemite-install-drive/
Best of luck!