check crack on head

my XJ recently became hot. A little past the middle/ almost 3/4.

I was thinking that it is just old coolant. So it was replaced it. Now driving to Massachusetts, I noticed my xj was blowing smoke while im driving on the highway. I pull over right away. The temp was almost in the red. I had a jug of water so i put that in right away and went to the auto parts store. Pulled out a hose connecting to the radiator and notice that it was milky.
So first thing that comes to mind is the head gasket.

The coolant/water was leaking so bad that I couldn't even put jugs of water in there to get back to NH (state next over).

So which way should I go about doing this??

What should i check first and how ?

I have looked all around this problem and hear that it's the head gasket. How do i test a leak there. And what happens if i have a warped head? Should I just replace the engine ??

Any help would be appreciated !!

Can you provide a little more information on the truck....year, mileage, etc?

it is a 97 with 142k on it. I haven't replace anything in that jeep except for a couple of minor things. It has been good to me It is a 4.0 with an auto .. anything else ??

I asked because the 0331 cast heads are notorious for cracking between the 3rd and 4th cylinder, but I don't believe they are in the 97s.

When I checked mine (which has the 0331 head), I bought a bottle of the flourescent die and put it in the coolant and let it circulate. Then I popped the oil filler cap in and shown the UV light to see if anything glowed. Anywhere the antifreeze with die in it is, it will glow and you can find leaks.

My 97 started running hot and cracked between the valves at the #1 cylinder at 148k.

I got a new head from Alabama Cylinder Head for $600.