Water filters carry $10,000 danger
You can buy the filter quite easily and a lot of people might know a lot about the filter itself but they don't know anything about fitting it - but give it a go anyway.
There is a lot that can go wrong. Ultimately, you are altering the plumbing system in your house. It doesn't matter if it's an under-sink or whole of house filter or one designed for an office building - you are altering your sanitary plumbing system and that can cause real problems that cost many times more to fix than just paying for a licensed plumber to install it in the first place.