I married a Indian Citizen while I was a Permenant Resident Card
Holder. Now, I became a US Citizen and changed my status to US
Citizen.

1) How long does it take to update the status from Permenant Resident
Card Holder to US Citizen? What kind of confirmation do we get? The
Notice of Action 797C or so was provided as a receipt to the petition
filed as a Permenant Resident Card Holder.

2) Once the petition is upgraded, whats the next steps and how fast is
the processing going to be? Any estimates for the spouse of a US
Citizen.

HI,
scroll down to the comment to the question linked below and click onto the site 
of the US Citizenship and Immigration Service.  Try FAQs and look for
what you need.  As the text of the question points out, you can get
differing answers from people selling their service on Immigration
matters.
I think you can find what you want.  If not, come back with a comment
and I will try to help.

And then I forgot to add the link:

http://answers.google.com/answers/threadview?id=511013