I only paids 113$ from rockauto.

auto zone cost $72.00 with life time warranty

In israel everything expensive :(

I have read through this thread and looked at the pictures but I'm having a hell of a timee getting at the heater core on a 2005 Lesabre. I have the dash completely disassembled and am looking at the air box. I can touch the heater core through the top of the box where the flapper doors are. I've tried to remove every screw I can find on the box and still can't figure out how you get inside to remove the heater core? Where does the box split, I don't want to break it but I am not getting inside the box. I have the entire box unbolted from the firewall and I can move it around somewhat but I left the AC hard lines connected so I wouldn't lose the charge but that limits how far in I can pull the box. Now if I can just get inside and remove the leaking core I can start to put this beast back together.

I am not sure what you mean by the air box. If it is what I think you mean, it'* the big black box on the passenger side inside the dash? You don't remove that.
You need to get to the heater core by laying down on the floor of your car and pulling it out towards the floor. First the black air ducts left and right have to be removed and a center one too which is difficult.
I wrote a whole guide above on the whole process.

Yes I am talking about the air box on the passenger side basically. The only thing I could find was some videos of the Century which isn't exactly the same as the LeSabre layout. I pulled the entire dash back to get at this box and now that I can touch it and take it apart I was trying to figure out where the box is split and how to open it. I have removed a bunch of screws that I have found and still haven't gotten into the core section itself. I noticed since I was already in this far that the fan motor has a bunch of leaves inside it, so at least I can get those out. I will say that the fan motor is one of the loudest fans I've ever heard in a modern car, if you turn up the fan speed much at all the thing is just so loud. Since an earlier 2002 had the same type of fan noise I suspect this is just normal for the design of the fan and motor.

The heater core is right in the center of the vehicle with some plastic covers over it.
You would benefit from a cabin air filter; no leaves would get into your blower. I added one to mine. It seems the cabin air filter was on the window sticker of many of these cars but no one on the forums has one including on my Limited.