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Replacing a failed switch is a combination of the procedures for removing a member switch and adding a member switch. 1st step of removing a member switch is turning it off but this is normally the case of a failed switch member, i.e. it's already off.
The important parts of inserting the replacment switch are setting its switch number to be the same as the member switch that failed and insuring it already running the same IOS version.
The combination of setting the replacement switch's switch number and IOS version is the "correct prep".
In theory, if the IOS versions were different, if the IOS supports auto upgrade, the switch might be connected into the stack without first insuring its IOS was the same version. Also, if there's a switch number conflict, most likely the replacement switch will automatically get the failed switch's member number, but it won't change if there's no conflict. I.e. it's possible, unless you set the member number before hand, it will join with the wrong member number. However, you can renumber stack member numbers after the fact but will need to reload them. Also in theory, I believe the renumber member switch, again if same model, should inherit the prior switch's port configs. Also however, I recommend insuring the IOS and switch number before you connect the replacement. This both to avoid possible issues and to minimize the actual time needed to actually bring the switch member on-line when you actually connect it.
If the switch is the same model, the stack should already have the failed switch's port configurations and will use that on the replacement switch.
Then you just place the replacement in the stack, powered off, connect the stack cables, as they were on the failed switch member, power it on, and it should join the stack and become what the failed switch was.
The disconnecting the failed switch member and connecting its replacement is the "it's pretty easy".
BTW, if the replacement switch is a different model, it's not that much more difficult. In that case, you can just add the replacement and will need to configure its ports when it joins the stack. Again, you want to insure the same IOS version and to set the switch number first. You can also drop the provision information for the failed stack member, define the replacement stack member model and provision its ports before you add it to the stack.
