In my case, a DYI filter change was 4 times cheaper than the suggested price by both my garage and dealership.
To buy a proper filter you need to know your car's manufacturer, model, trim and year. Many online stores provide a suitable selection of accessories for your car after submitting this information.
It is recommended to change the filter every 30000 km or once a year (unless stated differently by car's or filter's manufacturer). Quite often the smell in the car, specifically from the A/C, can be eliminated by replacement of the cabin air filter.
Let's do it!