Well it make it much easier that you don't have fish in the pond at present.
No need to empty and start over.
From experience I would add a pound (or a box) of baking soda per 1000G every 2-3 days to start. Keep checking parameters everyday until kh is at 150-200 range (then stop adding baking soda), nitrites and ammonia goes to zero.
There is an alkalinity calculator here but I have no experience using it. I believe every pond is different and the rate of how much alkalinity you pond will use up will depend of many factors. That is why you need to check KH frequently in order "to know" how your pond is behaving.
This is what to use (I get from costco in bulk):
While you are ordering all API test kits (online I assume), might as well order this: