How to download and use savegames on xbox 360 for complete beginner question

I often have difficulty progressing through the games as my interest is mainly in following the story not killing enemies or solving puzzles. Many games have no difficulty settings or cheats. I have now discovered a way around this: to install saved games downloaded from the internet using Modio. I tried this with a game when I accidentally deleted the only saved game and was obliged to return to the start. However I found that my profile and device numbers seemed to change every time I followed the procedure and then the rehashed and resigned save was not recognized by the console when USB was reinserted. I have already wasted hours struggling with this and can find no relevant solution online. Could you please answer these questions:

Do I need to update my 360 to the latest version to configure USB for transfer of the saves? If I do will I find any tiresome “improvements” to the console’s performance that I would be better without? Do these saves work if you follow the procedure outlined in YouTube videos on the subject?