I don't mean to be a bummer. You will want to get those heads check for warping. It's most likely not just a head gasket.
I just had the timing cover off my 3.7. I had the passenger side secondary timing tensenior go bad and had to replace it.
I didn't get a chance to remove the chains, which you will need to do in order to remove the heads. I did have to chase down a HLA that went bad as well. This required the removal of the rocker arms.
You might consider getting miller special tool 8516. This makes removeal/installation of the rocker arms much more easy:
I also discovered the 'loan a tool' damper installer did not work. The fitting on the end won't slip into the crank. The factory bolt wasn't long enough to get the damper started. So I picked up a 40mm 1.5pitch 120mm bolt. I had to order on line. This allowed me to get the damper started without beating it with a hammer.
Fair warning. If you remove the secondary tensioners there is a plate behind them. So be careful not to let them drop into the oil pan. I didn't remove the primary one so I have no advice on that.
Finally, the timing chain cover doesn't have a gasket, special RTV is used. There is a kit at the local parts stores that include the 3 'o ring' gaskets for the water passage (one is not an O ring) and the right gasket RTV. The service manual said not to use 'oil based' solvents. I used rubbing alchohol and a dremel with a polishing brush, the white one, nothing abrasive.
Although I tried to drain the cooling system I still had coolant run into the engine when I removed the timing cover. Probably about a pint or so. So I drained the oil. It sat for a week or two before I got to draining it so I am pretty sure the water went to the bottom of the pan. I actually jacked up the front the the truck a little to help out. I loosened the bolt a little and let the water drain out. Once I saw oil I opened it up and let it pour out.
Good luck gettig the heads back on with the engine in the liberty. That looks like a tight fit.