It isn't that hard. the difficulty is the same as on the normal mode, except you can't die. Your savegame will be immedialtely deleted.
So it's a good idea to copy your save game to an USB-drive every 2-3 levels. For the last 5-6 levels I copied the save game after every level I gained.
I only had to recopy my save game once. I played the first 15 levels on the normal difficulty, the last 15 on 'beginner', because that's when I had to reload my save game from my usb drive.
I played with the biospecialist, but you should play with whatever charactar you like most.
I do recommend playing the normal campaign first so you can get used to the gameplay mechanics.