88 Maxima AC Issue

[Future240]

So when I put freon into the system, it blows cold for a while, like 5 mins, then it starts blowing freon into the cabin. Freon can also be seen leaking out of a small hole in the firewall. I've checked the hoses on the compressor, condenser and the evaporator, and they are all fine. Problem seems to be what the repair manual, calls the AC Unit. I can't seem to find this unit anywhere for sale. Suggestions?