changing spark plugs

disconnect all cables to start with each one individually, and then move to the next spark plug, engine must be turned off and the earth wire must disconnect for safety's sake

Thanks for your reply Its just that being Volvo you can not see plugs wires or what modern tech is hidden under the cover when you gain access. I am worried there might be some thing I could do to upset coils and computer if not done the correct way.I have done nearly all my own engine work in the past but its been on vehicles with carb and no computer.To be honest I think Tech is a money pit for people these days.

Thanks again Imogene NZ