New locks and ignition barrel

Hi all, I am very new to this so apologies if what I am asking is a bit basic! I have a 2007 90 and only have one key for the ignition, previous owners must have had the door locks changed also as they are different to the ignition key. I have seen a kit advertised which has three barrels and an ignition barrel with two keys. Ideally this is what I want so that I only have to carry one key and have a spare if I need it. How big of a job is it to change the ignition barrel and the door barrels? Is it a job for a pro or could a relative amateur do it?
Thank you for all your help and again sorry for the basic question.
Toby

I know on older models ignition and door keys are different, may be the same for yours.