backlash1

It all depends on how much time and money you want to spend on your car. Your first option: If you want to recode all your barrels to the ignition key, you'll need to remove the door and boot lid trims to access the barrels. Once you remove them you'll need to take all 3 together with the ignition key to a locksmith to get them recoded. It is possible, if you have some knowledge and a lot of patience to recode them yourself, but I don't recommend this to anyone unless they've a bit of an idea on how to do it.
Your second option: You can also remove steering column shroud to access and remove the ignition barrel and get this coded to your doors and boot. If you do it this way you'll first need to have a key that works on your doors and boot, so
Option three: Remove the lock from the boot lid (easiest one) and take it to a locksmith and ask him to make you a key for it, and that should work on the doors as well. Once you have this key you can recode the ignition barrel to it. This is probably the option that involves less work for you BUT you have to consider if the previous owner may have a key that will give him access to your car.
Last option: Buy a set of barrels from Ford or wherever and fit it to your car. the set comes with both door barrels, the boot lid barrel, the ignition barrel and 2 keys.
So there you go. Pick the one you want and go with it. cheers
Marc