Welcome to the Bunnings Workshop community @Horvatmartin. It's a pleasure to have you join us, and many thanks for your question about installing water filters.
It would be best to check with your local regulatory authority to determine if a plumber is required to perform this installation. The installation is relatively straightforward, and how easy it would be will be determined by your skillset. We offer a convenient installation service where you select the product you want and arrange installation at the Special Orders desk. A qualified installer will contact you within two business days to arrange a time that suits you for installation.
I've included a video below of the installation process for a 3M under bench filter. Hopefully, it will let you gauge whether this is something you wish to attempt yourself.