I don't think removal would be that big a deal, but installation is likely to be a PITA. There will likely be 'gotchas', such as a needing a different radiator(condenser), and possibly a reflash of the ECM for stuff like rad fan control. And if the power steering line needs to be removed in order to get the A/C lines in, that would not be good because I'm sure yours is well along to rusting out just like mine did. And there probably will be other stuff as well.

I also have no A/C in my '05, and have never considered installing A/C (approximately the same climate as your area). With a limited future for the vehicle, why not just continue to keep the windows open, as you have always done in the past?