3070 water block GPU. What do I do with it?

I've been looking around for a decent second hand gpu for a while, found this Asus EKWB 3070 with the water block for 170€. I do not know anything about water cooling. Is this a good deal? What else would I need to get it functioning? Do I need a whole system with a pump and a reservoir or can I go with just a radiator? What would be the cheapest option? For context, your usual 3070 goes for around 250€ used here. Any advice and help apreciated. Much thanks.