I have found when getting quotes for anything, when the quotes get unreasonably high it's another way for the qouter to say NOT INTERESTED. They always will pick an unimaginable figure that you will run from.
Awesome!! It'll be interesting to see what condition the shell is in.
Word of Caution - Have them dig it out slowly and look for any holes punched in the shell. Start in the deep end. Get the main drain cleared, open it up and look for a hydrostatic valve. If there is one in there, open it up immediately but also be prepared to punch at least two 2" to 3" holes in the shell. You do not want an empty shell with no way to equalize water pressure. I have no idea what the condition of your ground water is but I have to imagine Louisiana is quite a bit more moist than Arizona. If that pool were here, I wouldn't worry at all about ground water (most people have to drill down 200+ feet to get to ground water around here) but it's not. If you do excavate it, it's going to sit open for a long time while you work on getting it restored. There needs to be a way for ground water to flow into it if it gets high enough or else the shell will pop out of the ground like a boat.
While i agree that you are probably ok, ground water and sea level can be 2 completely separate things. Think of all the lakes, streams and whatnot atop mountains.I don't know what the current water table in the area is, but our house is on one of the highest neighborhoods in the area (that's right, a whole 31ft above sea level). Many of the surrounding neighborhoods are at 24ft or below.
Might be free meals and a roof over your head for 35 to life if he IS down there.You know....free excavation