Hello and welcome! Well, you must have done some homework since you're waiting to add fish! Good for you!
First thing I would say is don't overstock, especially since you mentioned koi! They get BIG! Go slow, and don't over feed!
Here's a link to give an idea of safe fish loads :
http://www.your-garden-ponds-center.com/fish-load-calculator.html
Get a water testing kit (liquid is more accurate than strips) and use it to monitor your pH, ammonia, etc. It's easier to correct a problem if you catch it early, instead of waiting for bigger problems to start -- like dead or sick fish!
Oh, and from this point onward, you should consider a quarantine period for ANY new fish you add. No matter where they came from (store or established pond).
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Tell us a little more about your pond. It's 1000 gals, but how deep is it? What kind of pump & filtration do you have? Full sun? How many fish are you planning to have? Plants or not?