The exemption applies to the years the property was your principal residence, so if you owned a second property at any point, or converted part of your home to rental use, the calculation gets more specific and is worth confirming with an accountant before you list.
Downsizing itself does not trigger a tax event on your principal home, but the sale proceeds still pass through legal closing, and Saskatchewan transactions close through a lawyer, with legal fees typically running $800 to $1,500.
Confirm your specific situation with an accountant, and start with a hand-reviewed valuation so you know what you are actually working with. Get your hand-reviewed valuation from Joel Dyck.