My 4/4 2008 also has a CHBB engine which has the cam chain drive (not rubber belt) so you should not have to change that. BUT Please double check with MMC as I am NOT sure of the year chain cam drive was introduced.
Plug change isn't difficult but you will need a long reach box spanner. Make sure to grease the sliding pillars frequently. If you have the plastic type original radiator beware its prone to leaks developing and the top hose pipe exit failed on mine. Aluminium Mulfab radiators are the answer. My Duratec engine has now done approximately 85,000 miles and its really sweet.
If you have the 1.8 there is a little tweek you may like to try that's not too difficult . The buttefly valve air intake in its original form is prevented from fully opening in other words it's de-tuned. A file is all that''s needed to remove a small corner stop that will then allow it to open properly. The original post on these pages tells how to do it in full detail.