Andrew welcome to the PB Forum. The guys at SE Pond, as Yolk Sac notes, will do a good job and there are others. However no one cares about your pond/lake like you, the owner. Learn as much as you can here and elsewhere and be an informed purchaser of lake management services.

If you call SE and explain the situation -- that you may need stocking help, the lake situation including the spring output as Dave suggested - they will probably come and take a look and make suggestions. While high flow springs can do just as Dave said it depends on flow rate , evaporation rates, avg. rain fall , the size of the lake and the watershed to determine if lime and fertilizer will be an option. The same applies to fertility.

The part about a self sustaining fishery (little or no management) is not as easy. Pond balance requires effort if you want a good fishery. It is rare to hear about a stock and forget lake with good fishing. I have not seen or heard of one. You can plan in that direction by your choices of fish , harvest and fertility matters.

This Forum is a good place to find guidance on those issues. Try to write out your goals for the pond , like fishing , harvest, recreation , swimming , beach , pier , power available etc.