Hey at least it's a 4cyl. You can pull the head off yourself and bring it in to a shop.
Coolant loss and white smoke are good signs your HG went south. If you don't have water in your oil yet you will in a day or two.
I just went through this with my 88 4runner last week.
I'd quit driving now and pull the head off before you damage the engine.
Reman heads for your truck aren't too spendy. 3 to 400 last time I priced one (aluminum head builders in Portland OR is a good shop).
If your head is still good a cleaning, resurface and valve adjustment can be done for 1/2 the cost of a remanufactured head.
Good luck, be thankful it's not a 3.0L V6.