Well done on cleaning the filter.
With power filters you can wash the sponge in a bucket of tank water, then tip the dirty water out and give it a second rinse in another bucket of tank water if the sponge is really dirty. They can look clean but if you squeeze them a few times the gunk starts to come out and I have seen the water turn black from a clean looking sponge.
The filter case and motor can be rinsed under tap water. The impeller (magnet with 3 or 4 plastic blades on one end) can be washed under tap water too. Be careful removing impellers and impeller shafts. The impeller shaft can be made from steel or ceramic. Ceramic shafts can break if you are rough with them. Impellers sometimes have a small plastic washer on either end and if you lose the washer/s, the pump won't work that well so look out for them and don't wash them down the drain.
I reckon your folks are probably seeing you in a new light now you maintain the aquarium (water changes, cleaning filters, feeding the fish), your doing well.