you doing the research and showing positives and negatives is a good thing, people going by what other people said it is shitty.
Geo-thermo is much more cost effective down here than northern states, due to the huge delta T. I would recommend going to a heat pump system more than anything.
The funny part is most of the insulations values that where used when that was built, a R-30 roof, R-15 walls in now either code or worse than code.