Possible leaking Heater Core

My daughter has a 01 Neon SE w/ 107k miles on it. Today while driving she noticed some steam coming from the front passenger side carpet. When she got home I went out and checked the carpet and could feel that it was damp. Does this sound like a clogged / leaking heater core? If so, how hard is it to replace the core in a Neon and can someone hook me up with some detailed instructions ?