Civic - Honda :: 1997 - Cylinder Head And Gasket Replacement

I have a 1997 Honda Civic that I was given by an elderly neighbor's daughter after the elderly lady went to the grocery and ended up 100 miles away when she could not figure out how to get home. The car was smogged at the beginning of the year but when I got it ran very rough and the temp went nearly to overheating on the drive home when I was stuck in stop and go traffic.I found the radiator fluid level low and an oily residue inside the radiator water bottle. I took it to a mechanic to check it out and was told it had a blown head gasket and maybe worse.

I am thinking of buying a rebuilt cylinder head and replacing it myself but I am not sure how to diagnose if any other damage could have been caused to the engine. It's hard to know but I am guessing that the engine was damaged during the 100 mile road trip due to low coolant level. It turns out short term memory loss was the diagnosis for my elderly neighbor. I filled the coolant level and ran the engine for a bit and the temp stayed normal but the rough running remains. The oil dip stick shows no signs of coolant in the oil and the coolant looks bright green when I looked in the radiator after topping it up with some water.

Any way to detect if I could be facing bigger issues like failed bearings? I am OK to do the head replacement but an engine replacement starts to get into the realm of what it would cost to get another car of the same age.