I did it.

Corbin, yes. Gatsu. It isn't that bad, even considering I didn't play Ep2 all the way through before. Most of the time you leave the gnome in a safe spot while you clear out enemies. There are two really tough sections where you will do frequent saving and loading. One if the driving levels because the gnome falls out so easily. Though most of the time you can leave the gnome somewhere, drive, hit a load point, then go back for the gnome in safety. The helicopter always fires at the car, not you. So you can leave the car somewhere and go on foot to place the gnome somewhere safe. The other tough part is towards the end of the driving part when you have that standoff in the large house. You have to put the gnome somewhere safe since there will be a lot of hunters and grenades going off. I did take the gnome with me into the antlion den. Stupid. I found out later I could have left him with the dudes healing Alyx. Since you can't run while carrying the gnome it made an interesting partner running away from the commander antlion. For those int he Steam 2o2p community you should be able to check out my achievements :)

Dito, I did it on the PC.

Dito, also I do achievements for the sake of doing them. I don't care about the score. The score is meaningless.