If you want to totally strip it and start from scratch hoping any possible greeblies are killed in the process, I would do it this way (others may have other, and better, ideas)...
1. Turn off the equipment (heaterstat, filter etc)
2. Remove the fish
3. Remove the plants and throw them away (if you think they are infected with something)
4. Empty all the water out
5. Thoroughly rinse the gravel then boil it. Same with driftwood and decorations. If they can't be boiled, sterilise in bleach solution. Rinse really really well if you use bleach.
6. Wash the tank out with salt and water, rinse thoroughly afterwards
7. Wash filter and media in bleach solution. Rinse thoroughly. Spread media out in sun to dry out a few days.
8. Set it all back up again.
Oh, I would also wash the heaterstat etc with a bleach solution too, again rinsing very thoroughly.