I'd start by draining it with a trash pump. Then come in with an excavator and remove the undoubtedly huge amount of organic waste that has accumulated on the bottom. A large back hoe could likely do the work in a pond of that size.

Will a pond that small support fish? Well, as is a common answer on here. That all depends... Which species of fish? Fathead minnows or gamefish? If you want gamefish to survive in a smaller pond in your part of the country, I'd shoot for 8' and preferably 10' or even 12' maximum depth. I'd also have winter aeration. With depth and aeration, I think you'd see gamefish survive even your harshest of winters.

As far as what to stock, I'd look into a put and take fishery consisting of non-reproducing or minimally reproducing species. Utilizing single sex fish would be a good idea here...

What species are you interested in having?