PIC32MM bootloader process explanation

Hi, Everyone! I`m making my own bootloader system. I want to use extenal flash to load the new program runtime, reset the controller and load it to the uC flash. So there are multiple things I don`t fully understand.
First: About the .hex file. Can you tell me where I can find info about the structure of the HEX file? I suppose every row starts with ':', address and info. But this is just a suggestion. I think I should remove the rows which are going to affect my bootloader section, so I need a way to determine which are they.
Second: I`m looking at EN1388 framework.c file. There a special interface is used to transfer the hex file to the controller. I don`t need that. I can do it run time. But I need to know if there are sections into the hex file row containing CRC, different type of records and so on. Or it is just pure address + data?! 
Thanks!
 

In my system the bootloader skips over the hex rows that would cause a problem.

Ok! A simple question, just to be sure. I am writing my functions for decoding Extended Segment Address(02) and Extended Linear Address (04). So in case of 02 package the ext_seg_addr should take the 2 bites from the package is put them is between -
0102 - package bites
ext_seg_addr=0x00010200
and in case of 04 should put them like that- >
0102 - package bites
ext_lin_addr=0x01020000
Is that correct?
I`ve noticed the memcpy funct writes the databites from the liest significant->
data->01020304
memcpy(&dataholder,&data,4);
->result dataholder->04030201
Is that correct?

Hi! So I`ve written my bootloader and now I have to modify the ld file. So I`m folloing the instructions int the AN1388, but I don`t know how to determine how big should be the bootloader area. The document says I have to put the main program in a different area so the bootloader can erase only it. Where should I check how big is my bootloader?
Thanks!

Just a second! Stupid question again! As far as I understand I have to compile the project twice - first only the bootloader(to see the memory usage) and then I add the rest?
Thanks!
PP: I haven`t done this before and I`m a little bit confused!