When my heater core went out I also replaced the evaporator. I'd previously pulled the dash for the blend door replacement and didn't want to have to do it a third time. Since you lose the freon when you remove the HVAC I thought it would be a smart move. My only regret was not also replacing the foam gasket on the HVAC casing. After 11 years it was pretty well shot, now my wife complains about cold air around her feet while at highway speeds.
PS: Would love to tell you it was a simple 3 hour job but with me doing it solo and fighting my bifocals it was a two day project...
2004 WJ Limited Overland
4.7L HO, Black, 4X4 QuadraDrive w/Vari-Loks
Past Jeeps: 2001 WJ 4.7 Ltd / 1999 WJ 4.7 Ltd / 1993 ZJ 5.2 GW, 1988 XJ 4.0 Ltd