The officer corps used to be Maronites. They were replaced primarily by Shiites during Syrian control. There is a sizable number of Shiites in the Army. I don't think they'll join up with Hezbollah, but I simply cannot imagine that they would not put up at least a token resistance to an Israeli ground invasion, if only to save face.
The officer corps is still Marionite
Their version of token resistance would be to instruct their soldiers to fight valiantly while they prepare to rush to headquarters for further instructions -- incidentally taking with them a nice change of civilian clothes, a passport, and all the money they can beg, borrow or steal.