You can guess all day long, but without diagnosing with the proper tools, that'* all you'll be doing ....guessing. I always lived by the rule that a nice looking body and interior alone is worth $500. If you have the time and tools and space of course, it could be a good investment. If you could put a compression gauge on it and see what the cylinders were running at, it would be a good indicator (two adjoining cylinders lower than rest), or I've even seen a radiator pressure gauge indicate a blown head gasket for it would jump when the guilty cylinder would go into its compression stroke. I had one that was so bad (head gasket) that it would pressurize the coolant system to where it would gurgle air bubbles into the coolant recovery tank after you shut it off. I quadrupled my money on that one.
I wouldnt say it would be impossible to crack one of these heads, but unlikely.
I have seen a cracked head on a 3800, but its incredibly rare.... Usually the head gaskets will blow before the heads will crack... I think she is going to find a blown head gasket or gaskets.... But As stated by another, if there has been coolant contamination in the oil than this is something that the bearings in the engine will not tollerate too well... If the oil and coolant mixture has enough time to become acidic than the bearings in the bottom end of the engine will be pitted for sure...
And I do agree though its a good investment... Even I would be willing to but it and replace the engine in it... In really good shape, $300 than $600 or $700 for a decent engine without a billion miles on it... and still make a good bit out of it... Or keep it...LOL