What kind of pump; submersible or shallow well jet or deep well jet?
You will want some kind of control on the well so you don't run out of water. There are things like the PumpTec that protect a submersible pump, but you don't want that to be your controller.
Your controller should put water to the pond only when there is plenty of water in the well. I would not replace the pump until I found out if I could pump it dry in the summer (when you need the water in the pond) with the existing pump.
If it is a submersible in a 4" casing you should be able to put in a pair of miniature float switches that can be set a few feet apart. Open the valve to dump water to the pond when the water floats the high switch. Run it until the water drops to the low switch, and don't start it again until it floats the high switch. I can send you a control circuit schematic and parts list if you need it. The switches can be assembled on a weighted rod and suspended from the top with the signal wire. You will need 3 conductors in the wire. The switches and control including a solenoid valve to dump the water should not cost more than about $100 plus wire down to the operating level.
Find out how deep the pump (or pump inlet) is, and how far to water. Then, pump find the pumping rate and the drawdown over 12 hours of so of pumping.
You may want to get a water meter so you know how much you are pumping. They are not that expensive. It will take 20,000 gallons to put 1" of water in your pond.
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