I'm assuming that the little hose that goes from the top left of the coolant tank to the little black nipple on the upper hose is the vent hose. ??

If so, can I just plug the hole where the black nipple thing used to be and run the hose to the ground until I get a new upper hose?

 

Possibly, but you may well get codes.

If it's a 3.0 (worth adding to your sig) all the lines are shown in colour etc in the stickies.