The aluminum alloys used in cases are quite ductile so local temperature gradients aren't a concern. One potential threat is reduced temper in the case alloy but one would have to get the aluminum very hot (500+ F) for that to occur. You just warm the barrel of the crankcase evenly until the liner slides out. It shouldn't require much. The idea is to have the liner at 40F and the case at 200F. With that temperature differential the heat will transfer to the liner very quickly so work fast or you'll have to start all over. This technique has been used for generations of automotive engine rebuilders to remove stubborn crank pins from aluminum pistons. It's where I acquired it.

When replacing the new liner cold soak it in the freezer and heat soak the case in the oven at 250 and they should go together without fuss.