I recently sterilized a tank because it had an unknown pathogen that I couldn't eradicate. Here's what I did:
Remove all fish and put in a QT tank.
Remove all wood and rocks from tank.
Remove filter sponges, rinsed out well, let them dry for a few days.
Add a gallon of bleach to tank (90g tank) and let run, stirring substrate in tank.
Dip rocks and wood in bleach water for a few minutes to be safe.
Drain tank and refill. Drain again, refill, and add dechlor.
Add sponges to filter from healthy, established tank.
Add all décor back to tank.
Let run for a day, then add healthy fish.
I did this several weeks ago, the tank is now running fine with 12+ fish, no deaths. Anything you let go completely dry will be pathogen free, it can't survive without water, but I bleached them just to be safe. I didn't bleach the sponges because they will deteriorate quicker. Once I knew the sponges were dry, I put them in the tank I swapped sponges from, and that tank has been healthy during this period too.
I don't think boiling is necessary, but it can't hurt. KISS tells me bleach sterilized everything, and that's all that's needed, but do what you need to for peace of mind.