Sparkplug coil pack help?

Help please so the code was a failing sparkplug or coil pack number 1......do you guys chsnge all 4 sparks and coils or just 1or change one coil and all 4 sparks??
Also is eurocarparts coil pack ok? Same as oem?
 
You should try and change one by one .
And i would go for oe .
Especially when its not that pricey(about 30quids for coil)