The assembly w/ 4th stalk is $40 more, but you do need to spend about $10 more to buy the necessary molex connectors and wiring to make up the harness, also, you need to have the OBC turned on (already to go if you currently can display outside temp). Some dealers will do it for free while others charge to do it.
Not to worry about the gauge or cluster, it's a simple hack.
Not understanding what you mean by the ground on the clockspring, but if you mean the 2 plastic posts I would replace it. It is part of the airbag system - the contact spring to be precise.
