If you want to take the tank down then you can rinse everything in white vinegar and then rinse under hot tap until you don't smell vinegar, let air dry.
Or if you want you can do Bleach dips. Basically get some Clorox Bleach, do a 1 parts bleach to 19 parts water in a bucket. You can let all ornaments/fake plants/equipment soak in there, not the gravel though. The gravel can just be completely dried out and will be safe again, or sand if you have it.
But for the solution, let everything soak for an hour and then rinse under very hot tap water until you don't smell any bleach. Then either rinse that bucket out real well or get a different one and then just fill with hot tap water. Throw everything in, let sit another hour. Rinse again and this time, use warm water and 4-5x the conditioner in that bucket. So if 1 drop is needed, use 4-5 drops per gallon in that bucket. Let sit and hour or two and dry out, stuff is now ready for aquarium use.
For the actually tank just rinse out with white vinegar and rinse out with extremely hot tap. Let dry, fill with water, use the 4-5x conditioner for that tank and sit for an hour or so. Dump out and rinse with hot tap water, and voila your tank is ready for new fish!
If you have a filter, you can get new cartridges and soak the filter with the rest of the ornaments. Rinse the carbon and just let that fully dry in the sun if you can and that should be fine for use again