Hello and welcome to the forum. Your car looks great. I saw the car advertised on ebay. Love the sunroof and alloys. Okay, what to watch out for re watercooled Bis. Reputationally, overheating comes to mind but I have yet to experience this. Keep an eye on the temperature gauge. Check that the radiator fan works and switches on automatically. Check the thermostat is working, though other members removed the thermostat. I have kept mine in with no problems. There is a lot of thread on these (use the search function). Watch the light on the dash, may indicate that it needs topping up (please refer to the manual). Yes, the kingpins need to be greased regularly depending in usage.
With regards to spares, Blonde126 listed a good selection of tried and tested suppliers. I would not bother lowering the car (that is just me). Yes, the car gets a lot of positive attention which is great! Most of all enjoy driving it!
Check out the meetings/events! We'd love to see you and your car! Please post some photos of your new car!!