I only know about my 98 rodeo, but I wouldn't pay $350 for a heater core. When I repaced mine I just went to a local junkyard. Heater cores are rarely ever damaged in an accident. I think I paid $35 dollars. You do have to tear the entire dash apart to replace it. It's not terribly difficult; just a lot of work.

As for it being a "heating unit", mine looked just like every other heater core I've ever seen.