While your under your hood pop the intake beauity cover off and take a look below the intake. If you see coolant your going to need a intake/vally pan reseal. Its very common on 4.4's to have that leaking. But back to the point, while under there get a flashlignt and in the front left of the intake (the side of the oil filter) you can see the vally pan bolts, coolant usually collects there.
Before you go and replace parts I havent read of up your post but have you started on that 60k tune up yet. if so I would go over my work again if you replace the rad hoses or anything else coolant related.
And buy 2 gallons of coolant.