Lexol (neastfoot oil) is good stuff. I use saddle soap as a cleaner, lexol as a conditioner, and Sno-Seal as a waterproofer. Those three things keep what I have in really really good shape. Never tried to bring anything back from the grave though.
Don't know how rural you are but find a "horse store" (you know, boots, saddles, tack, all your horse-people stuff) and take it in.
They'll know someone who can "redo" saddles...and those guys can work absolute magic. If you don't want to get that involved they'll likely have and know just what you need for a DIY.
That group spends a lot of money on leather-made equipment and they know how to keep/repair it.