Done! Tks!
First came to the back of the Sears in Rideau, where there's a mini watch repair. The man in charge didn't ask anything before attempting to use a knife to open my watch. He doesn't look like professional and I told him I will go somewhere else. Frankly I don't want my favorite Swiss watch being damaged.
Then went to the WalMart in Lincoln Fields. Unfortunately, no matched battery is sold and the clerk suggested me go to check with the 3 Jewellers upstairs (the 2th floor). I then looked around.
The first Jeweller I went in was served by a young lady. She told me it is easy and charges include tax are $7, applicalbe for any kind of battery. Facing a girl who looks like a part-time staff in her early twenties, I said thank you and went to another Jeweller. I want someone who is more reliable to take care of it.
Finally I had it done in a Jeweller looks more decent, located next to the SubWay (fastfood). A man in his above 50 changed the battery in his mini workshop and told me it was 1 year guarantee. Total charge was $6.9, and the receipt showed "Lincoln Heights Jewellers".
Hope the above helps people concerned.