"Basically my question is, should I take one of these mulies and not worry about the genetics growing in the area?"

I would say that the genetics are in the area already. And will stay there as long as bucks reproduce. The larger bucks have left their "seed" in the smaller bucks, which will become larger bucks next couple of years right?
You are talking about selective harvest when taking one (or more) of the larger bucks. I say it is O.K. Not knowing anything about the area, (rolling prarie, rimrock bordering pasture, property bordering Public Land, animals migrating through or holding up, etc??), you say it will be developed in the next couple years. That tells me to enjoy the harvests now, because those animals will likely be displaced as the developers move in.
A 1000 acres isn't a lot of land either. About 1&1/2 square miles. Chances are that mulies you find there are not always there, which means there are probably many others in the region but outside your boudries.

Bottom line . . . You are not going to ruin the area, the developers will do that for you. So take advantage of your quarry while it lasts and enjoy the hunt.