I've had a used Focus for over a year now which until the weekend hasn't had any mechanical problems.

The car unfortunately is now shaking when idle, and the engine warning light is lit on amber.

I bought a set of new spark plugs from Euro Car Parts yesterday and went to change them however the socket I also bought snapped in half under the slightest twist so back to square one. I'm going to buy a new socket from Halfords tonight, however I've also just called a garage at the end of my road (who I don't really trust) and they've told me the coil pack and leads will also need replacing - is this true, or will just the spark plugs suffice?

Obviously I'd rather not pay a garage for something I can do myself.

Thanks in advance.