Most things then will still work -- not like there has been new GBA ROMs released (give or take some previously unreleased Chinese efforts a little while back but that is just another lost region duplicate of something that already existed). Equally the basics work on most devices -- tables, pointers, graphics and data generally share many of the base concepts. I will note though if you say 2011 then that probably means some of the later GBA pokemon tools which are great for pokemon but not much else -- other than maybe some Final Fantasy stuff then pokemon is quite the exception in ROM hacking as far as the extent to which tools have been made.
I have a guide http://www.romhacking.net/forum/index.php/topic,14708.0.html
if you want one that is specifically for the GBA and DS (they are very closely related).
GBA commercial games do not have a file system so you can't break them up into individual files like you can on floppy disc, CD/DVD and some later cartridge based efforts. Some GBA homebrew will use a file system though (see GBFS for one popular example). You can still find data easily enough though on commercial games (I cover tracing a bit in the guide but https://www.romhacking.net/documents/361/
is also good, though the debug version of http://problemkaputt.de/gba.htm
is what we tend to suggest these days instead of vba-sdl-h as used in that guide (if you can redo the things in that guide but in no$gba debug you will be well away to doing good stuff).