good idea with the acetone i might try that n see how that turns out n go from there.
I changed the heater core when i got the car like 4 years ago, only had to since i cracked the joint when i was pulling off the heater hose, did the core swap in a few hours once i got the a/c lines off. Wasn't a pain at all, dash stayed in the car, just pulled back the passenger side corner and got to it from there, also took out the glove box.