The previous poster is right on target.
I'm gonna add a little more.. sorry it's going to be a little long.
I have a well I use for my whole house,.. it's about 120 feet deep and has some of the clearest, coldest water I have ever drank.
IMO 30 or 40 feet isn't very deep,.. on the other hand, just depends where the water table is, or if there is an underground river.
If you want to use yours to irrigate your garden, this would be an excellent way to do so for practically no charge (the water you save on a water bill will WAY MORE than pay for the extra power you use.
Also you can have it hooked up to water your grass with just any type of lawn sprinkler. Again no cost, and your green grass would be the envy of the neighborhood (and strong grass helps to keep weeds choked out)
I'm not sure how to go about it (Maybe someone can interject here). But as an afterthought, I'd see if I could find out if the well is still working, has good water, etc.. I had to replace my well pump a few years back, and it costs about $300. (like I said I run my whole house off of mine though -- so you might could get by with a smaller (cheaper) one if you needed one. If the pump works, that would seem to be your major expense already spent for you.
I'D DEFINATELY check about getting this hooked up. I live in the hot hot hot South East U.S. like you do.. so all the cheap (or free) water we can get is wonderful. IMO I think it'd be a great investment in the long run - just do a little homework and make sure the well is useable... have someone with electrical knowledge look it over, etc
The system in the pics looks like it was put in by someone that knew what they were doing.. so I'd think it'd be easy to finish up where they started.
Let us know how it comes out.
OH.. couple more things.. Often around a well you'll see a "pump house". It's a small building that you insulate to put your well / bladder tank, etc into (keeps things from freezing during winter)
Very low cost.
One other thing about the bladder tank.. the bigger one you get the less the pump cuts off and on. Cycling off and on frequesntly is what wears out a pump / or burns one up causing you to have to replace it.
I have 100 gallon bladder tank in my home, and keep the pressure set between 60 and 80 lbs (on and off). My pump puts out about 6 gallons per minute... and a few weeks ago I ran it for 4 solid days without never turning it off. (I have lots of water)
anyway, I don't think it's necessary to run a bunch of piping back and forth from the well to your house. Everything can bunction right there where the well is at.
And where the Bladder tank attaches there will be a faucet (like that comes out of the side of your house) Some call them a hose bib I think.
anyway depending on the size of your yard and the distance from the well to the garden.. you can just hook up your hose to that faucet, and water the garden, grass, etc all from that spot.
I found this link that gives you a geberal idea how to replace a tank (or in your case how to install one) I am sure more searches can lead you to more info.