
Merry Christmas indeed!
How nice of that neighbor.
The tank can be sterilized using 19 parts water to 1 part bleach. You can put the heater in the tank (if it's the submersible kind) Rinse until you can no longer smell the bleach then OD it with dechlorinated water.
I've never sterilized a large filter. I'm thinking you can run it while the tank is filled with bleach water. Rinse as above then run it for a long time in the OD'd water.
You might want to wait for others to respond about the filter.
Good luuck.