Just bought a new-to-me 2010 ES and was only given 1 key fob from the dealership, the single previous owner only turned in one they said.
I've looked into getting a new one through a local Locksmith ($235+tax for fob, key, and programming) but I'm wondering if I should reprogram my original key while I'm at it?

 

I do not think there is any need to do anything with your original key. It is already programmed to your car.
You are just adding another key and it needs to be programmed to your car. The locksmith is programming the key fob, not the car. You can confirm this with the locksmith.