Yes, the common area for a 4.0 head to crack is between the valve seats, and yes, it goes into the water(cooling) jacket.
It takes a special skill to weld cast, but it can be done, new/used head would be preferred, but you go with what you got.
The crack will allow "air" to be pushed into the cooling system each time that cylinder compresses and then fires.
This will displace coolant in the head and make a hot spot until the "air" is burped by flow thru the head.
This compressed "air" also forces coolant in the rad out the overflow because added pressure exceeds the cap rating, so available coolant to cool the engine is less and engine starts to overheat.
So probably not a "driver" unless you want to stop and fill up with coolant all the time.
You can try a head gasket sealer, I used a Rislone product a few years ago on an older truck, sealed up the head leak for about 10 months until I had a chance to redo the heads, it was an older GM V8 used a few times a week to haul things, not a daily driver.
And no it didn't clog up the heater core or rad, lol.
I drained the coolant, flushed system with water, put in fresh coolant and added the Rislone, you run the engine until it heats up then shut it down for a few hours until it cools down.
When I started it back up no white smoke, no bubbling rad, no overheating anymore.
I left it in for about 10 months with no ill effects on the rest of the system, and I did check because I always thought things like this would cause other problems.
It didn't in my case, but can't speak for others.