I think there is no harm in sending an updated letter. But just make sure that there are no major differences in between the latest one and one you sent earlier.
Also, check this link for more details about where to send it.
http://www.cic.gc.ca/english/information/offices/canada/ottawa.asp#faq
Question # 6 in FAQ.
Scan and e-mail documents (other than police certificates) to: OttPilot-Immigration@cic.gc.ca
Send original Police Certificates to:
Case Processing Pilot – Ottawa
219 Laurier Avenue West, 7th floor, section B
Ottawa, Ontario K1A 1L1
Canada
**** If you applied at the Canadian Visa Office in Buffalo, New York, we have transferred your application to the Case Processing Pilot-Ottawa (CPP-O) for processing.
Also, check this link for more details about where to send it.
http://www.cic.gc.ca/english/information/offices/canada/ottawa.asp#faq
Question # 6 in FAQ.
Scan and e-mail documents (other than police certificates) to: OttPilot-Immigration@cic.gc.ca
Send original Police Certificates to:
Case Processing Pilot – Ottawa
219 Laurier Avenue West, 7th floor, section B
Ottawa, Ontario K1A 1L1
Canada
**** If you applied at the Canadian Visa Office in Buffalo, New York, we have transferred your application to the Case Processing Pilot-Ottawa (CPP-O) for processing.