$400 is good to get one off of Craigslist.
However, If you haven't kayaked fished before, I suggest renting one first.
It looks like you're on the right path. I've seen quite a few folks jump off the deep end and buy a top of the line kayak, only to turn around and put it up on craigslist less than a year later (all because they realized that kayak fishing wasn't for them).
I dont live in the DFW area, but I know there's at least 2 places out there that rent out kayaks.
Just rent one that'll fit your requirements (weight of you AND your gear, plus the height) for the weekend and see if its something you'll enjoy.