Need minecraft modding help.?

alright i have been attempting to install a friggen inv editor for quit some time now. I have finally found one that i would like to put in, however all this techey jargan is sucking my brain into a never ending pit of dispair from wich there can be no return. For example. what in gods name is a META-INF and how am i supposed to delete it? Another question is how can i find %APPDATA%/.minecraft/bin. i have tried just typing this in, however when i do my computor shows a blank... and as a last question if soemone could please explain a 7zip and wether or not i need one i will be extremly grateful.... thats pretty much it, thanks for your answers (if you do).