Replacing the badge is your personal preference I guess. You could add one from a Fairmont/XR etc but that would be ghey in my opinion (considering it wouldn't be one of the two). The other option is to bog it up and paint it as if it didn't exist in the first place
You can add an S-Pac dash as long as it's from the same engine type (I6/V8). Don't know if it matters if it's from an EBII-ED though. I think you should be right, as long as it has the Smartlock. Better get someone to clarify that for you!
In regards to aircon, my dad's getting his aircon fixed today, including regassing. The parts and labour come in at around $450 which includes regassing ($80).
Hope I was some help!