I've got an 05 plate 1.4tdci and had to remove the air intake pipe (a couple of screws and a wiggle) to get a socket into the very small area at the front right (looking head-on at the car) of the engine - unfortunately didn't have a socket large enough to fit it, so just leaving it until it goes for MOT in a couple of months. But providing you do have a socket to fit it should be a 15 min job tops. Use lots of rags so you don't cover the engine block in yummy old oil!
I'd love to hear of any problems with this particular model - haven't had any yet, but my Ka is rapidly proving to be rubbish body-wise!!
Jim, January 2009