Going towards Orlando, you would disembark from your domestic flight at Toronto and follow the signs for U.S. Connections. You would collect your Baggage in the U.S. Baggage Claim area. You would then pass through U.S. Customs and Immigration Preclearance and place your baggage onto another carousel to be loaded onto the airplane before proceeding to your gate.
CLARIFICATION: After you place your baggage on the carousel, you must clear security before going to your gate. This is important, because if you buy something to drink in Ottawa after clearing security there, you have to drink it all or dispose of it by the time you get to Toronto and go through Customs.
Upon your return from the United States, you would disembark at Toronto and pass through Canadian Customs/Immigration. You would then claim your luggage and follow the signs for Connections. At that point, you will put your luggage back onto another carousel and proceed to your gate.
AGAIN: You will have to clear security between the time you re-check your bags and go to the gate.
For more information, consult the website of the Greater Toronto Airport Authority on the subject
Connection Tips (
En français - Correspondances)
In addition, the GTAA has posted several videos on the process of moving through the terminal during your transfer process:
http://www.airportwayfinder.com/wayfinders/yyz/
As to how long it would take, I've never connected through Toronto to the US, so I couldn't say, I can't imagine you having that much trouble with nearly an hour and a half between flights, though.