Transmission Troubles

[Suidae]

2005 GT 3.8L SC. I got this vehicle into a LOT of water a few years ago, and the transmission went out. It has been sitting since. The transmission will work fine if you put it into low, take off, and manually shift to drive. If you attempt to start in drive, it acts as if in neutral. Any ideas if this is an expensive fix?
On a side note, due to setting so long, the AC has seized as well, but I know how to deal with that.

 

[melsg5]

did you check the transmission fluid to see if its is contaminated with water?
if you do have water the transmission has to come out and checked to see what has rusted internally.