Index plugs?

[fishingwithblue]

What does this mean? I have always changed plugs in my smaller motors but what does index plugs mean. My evenrude 200 DI is getting worse with cranking and idling. I want to change the plugs and clean out the carbs this weekend instead of having it serviced at the shop so it wont be out of the water forever. Honestly I'm intimidated of the 200 hp. Can anyone give me a step by step on:

changing plugs
cleaning carbs
changing/checking water sep

Hey Ferm, I couldn't find the Sea Foam, where do you get it?

Thanks a million!