Sorry to hear you are having trouble.
Since you are using a PAL system, you will not be able to directly update the game through your 3DS. You will have to download it on your computer using something such as FunKeyCIA or PlaiCDN. You will then need to manually install the resulting .cia to your 3DS using FBI. Additionally, while you won't be installing it, it sounds like you will also need to use these tools to obtain a copy of the Japanese 1.4 update.
As for difficulty applying the patch, it's not terribly difficult. Everything will stay in the same folder you extracted from the .zip archive, and the filenames you need are all listed in the archive. However, you will need the
RomFS of the Japanese game and 1.4 update,
not just the ROM (as in, you cannot use just the .3ds or .cia files). There are a great many resources here on GBATemp that detail how to obtain the RomFS files you need (
such as Asia81's guide and toolkit). If the .cia/.3ds files you have are encrypted, you will need to use GodMode9 to decrypt them before you can obtain the RomFS files. Be sure to check their MD5 sums using the included tool before attempting to apply the patch.
Lastly, as much as I would love to make this patch PAL/EUR compatible, it is impossible to do so. The PAL/EUR game never received an official eShop update, and without that, files added by this patch are not unusable. Specifically, the update added story flags and 3D model information that are required to properly load the files added by this patch. Additionally, if the PAL/EUR game does eventually get updated, but those things are for some reason removed, the same situation will apply (to clarify, even though they are unused in the official US version of the game, the data I needed was left intact, making this patch possible).
I don't plan on making a video tutorial, but anyone here is absolutely welcome to do so.
I hope this helps.