Hello,
Any thoughts on:

(A)
===
When spark plugs should be replaced on a 99ML320 ( I have 62K miles), and is it a DIY job, and if so, any idea on the torque that needs to be applied on the plugs?

(B)
===
Also, I have a 97 C230 that I am going to change plugs on. Any ideas on what the torque setting for the plugs on that car is?

(C)
===
Also, I'm buying the plugs thru fastlane. Are they already pre-gapped or do I have to adjust gaps. If so, what's the gap setting?

Thanks!