Mine is an '04 and I have 56k miles on it. I have no idea what it's worth. Yes, a baby seat would fit back there. When my grandson is with us, he makes my wife ride in back there.
The one downside to the Tacoma Xtra Cabs up to '04 is that they never made them with a third door. '05 and up with the new body styles have the doors for the jump seat area. Kids don't seem to mind climbing in there, but it's not easy for an adult. Accessing that area for child seats or groceries or whatever your hauling isn't too bad a task though.