OK, be very very careful doing this job. Removing the low pressure hose is the key to success or failure, and failure can mean a new evaporator. I have a proven technique for this that you may or may not be able to emulate.I have a helper brace the fitting from the passenger side with a big screwdriver or pry bar.I then take an air chisel, with a long bit, and just vibrate the large nut as if I was trying to turn it. Eventually it always frees off, and it can then be easily removed. If you do not have the ability to do that, you might well buy a low pressure hose and use a dremel to cut the nut by splitting it on one side. It is really easy with the limited space there to wring off the end of the evaporator.... The little coil fits into a sheet metal fitting on the lo pressure side of the evap fitting.It is held shut by 2 pozi driv screws. Loosen them, and the coil will pull out. Insert the new one and secure the screws.
Good luck!!
Jesse