Leakages in the external pipings of a freezer can easily be repaired by brazing (welding). The one you described seems to be in the foamed cabinet and hence, as bad as an internal leakage. This type of leakage can be repaired but a lot must have been compromised in the process, including the insulation. Its better you source for another freezer. However, as long as the gas has already escaped, you may not be in a serious danger anymore. Study how to dispose of an old freezer. Sorry.
Cassy, January 2009