Is it possible to check to see what kind of condition your starter and plugs are in?

I just bought the car with 80 Kmiles on it (Its a 95 Nissan Maxima SE) and in the cold it has some rough starts. I know I still need to clean the TB, but I want to know if there is a way to check the starter?

Also do you recommend replacing all 6 plugs? Any idea how much that will cost?

Anyone know what anair gap pipe and (end) rings are and if they are both rusted about how much it will cost to fix?