Thanks for your quick reply Leon.
However, i still have some doubts in my mind.
1. As you said, i think its better to inform CIC about my wedding plans which will delay the processing of my PR. But how do i do that? Just send a letter to CIC? Do i need to send it to Centralized Intake Office-Nova Scotia or CPP-Ottawa?
You send it to the visa office that is processing your file right now.
2. If i am adding the details of my wife into my PR application after marriage, doesn't it show that we are planning to stay permanently in Canada? You said that when my wife applies for open work permit, she should show that there is no risk of overstay. Isn't this kind of contradicting each other? Can you explain a bit more about this?
Temporary workers usually have to show that they are not a risk to overstay. However, if you are applying for PR and have reached a certain stage in the process, they know you are getting your PR anyway so they will not worry about overstay any more.
3. I hope i do not have to inform CIC separately in a letter that i will be out of the country for 1 month.
Inform them at the same time you inform them about the impending wedding.
4. Can you please confirm if IMM1295, IMM5645 and IMM5257 are the application forms for applying for spousal open work permit?
Right. Use the forms here: http://www.cic.gc.ca/english/information/applications/work.asp
5. Will there be any problems for my wife to get an open work permit because i am on a closed work permit?
If you are on a closed work permit with a skilled NOC, that is actually better than if you were on an open permit because if you were on an open permit, it would be up to you to prove that your job is skilled.