well depending on the linux os which you chose mint i would say thats more than enough although i have never used mint it supposedly not that large as well
the only problem i have had with partitioning is not defragging first and making sure what im partitioning is all free space making windows freak at next boot cause files were moved and other stupid things like that. i think we all would suggest gparted for partitioning which has a nice gui and is relatively easy to use as long as you understand the words it has on it
(like logical partition primary ect)
and no any harddrive/stargae device can be partitioned from a hdd to a sd card so no special hdd needed
and agreed a lot of linux apps have not great documentation but i have also seen the many apps that have had better documentation than windows/mac so i guess it luck of the draw X.x