GBA games have no individual files like the DS and optical media based systems. It is all in one and you get to pick it apart, and crowbar it back in later. Said crowbarring is usually not as hard as older systems as most games have oodles of space you can use.
A tile editor is good if you have to edit the font, if there is text as imagery (anything even vaguely fancy probably comes as an image rather than text, especially on lower text games like puzzle games and platformers), finding the font can also help make tables (it can give you orders of encodings, options for tracing sessions, elimination (if ? to ? is all the sprites for the game it is not going to be the text and you can skip checking that section for text) and more besides.
That said I had a quick scan of
8:59 has something which might be graphics, 11:47 too (and it appears to come up often enough), 22:45 almost certainly is (whether you want to translate it is a different matter) the UI elements might graphics (or at least a special entry as part of the font)
35:42 might have some things,
most of the text is likely just text, though the different colours might mean you have some markup to deal with (if you have every done HTML or manually made something bold on a forum or something then can be like that, except usually using binary instead)
IPS. Disadvantages. It is in place (any bit which is different will be detected as a change, where it might be just something shuffled forward or backwards a bit, or it might be compression you have decompressed and recompressed after your edits), though this is not so bad for the GBA but is fatal for the DS and said things with file systems.
It is pretty much limited to 16 megabytes. GBA games go to 32, though most are 16 or under and most people don't need to tap into the last 16 megs for their hacks.
It has no verification of the input file. Someone can then feed it a different version than what it expects and you get a "it does not work" post when it is their fault. Not a major problem on the GBA but on something like the SNES with dumper added headers it is a nightmare.
It has no verification of itself. If the patch is corrupted it will patch away quite happily and you are back to the "it does not work" posts.
It struggles to create data. Hard if you are expanding the ROM.
There is no one version of IPS. It was made by nobody knows actually and many have extended things over the years. For the most part this is a non issue as a basic patch should work on all, however some patch maker programs make odd things which other programs in turn struggle with.
It sort of just about works for the GBA but fails horribly after that. Rather than having a bunch of different formats though (
https://xkcd.com/927/ is so very true) many have taken to discouraging IPS' use wherever it can be in favour of something better.
I would not really trouble yourself with considering the merits of IPS at this stage though.
As for the document I did try to make sections and titles for the various things. The sections should be able to be read standalone and the introduction is there mostly to get you started with some of the concepts to follow.
As for figuring out what hex represents what I cover a bit of it, Japanese does not work for some of the easier methods that hackers delving into games using Roman character set type languages have but it is still quite possible.