You don't send the original receipt to your visa office! The original receipt must be sent to Mississauga, specifically at this address:
RPRF payments or other correspondence:
CPC Mississauga
P.O. Box 6100, Station A
Mississauga, ON
L5A 4H4
This is only because u are sending it later than the rest of your application. As for your wife, I believe she has been rehabilitated, which means she is ok to enter Canada. Even though it doesn't show up on her FBI report, I think I would still mention it, since they do ask for any crimes committed and charged for.... there are ways for CIC to find this out, so it's best to be honest and up front. You will have to explain the circumstances of the crime, etc. but since it has been 19 years since the crime was committed, it shouldn't have a negative effect on her application.
I'm sure others with more experience when it comes to crimes and rehabilitation will pipe up and let you know for sure. You might want to post this question also in the Spousal Sponsorship thread, because more people are likely to see it.