Sounds like you got lucky, in a way. At least it looks like nothing major. Once everything is cleaned up, definitely take a precision straight edge to check the head and block for warpage before going much further. Don't know the specs off hand, but usually can't have more than a couple thousands (maybe 3 or 4) variance. Since you have the cylinder head off anyway, I would do what whunter said and definitely take it to a machine shop and do a valve job (grinding valves and checking/replacing guides and seals), if your budget allows. Preventive maintenance. Using a 4-1/2" grinder with a fine wire brush, or hand brush, clean the head combustion areas to get them cleaned up. Cracks will usually be visible to the naked eye, but from the pictures, don't see anything major so far. Visually check prechambers to make sure balls inside are supported on both ends and not burnt and pitted. If they are not supported on both ends, the prechamber must be replaced. Also closely check end of prechamber that sticks into the combustion chamber for cracks between the holes. If there any cracks, this requires replacement as the end can break off and cause piston damage. Good job on the oil on the pistons. This should seep past the rings and keep them lubricated, hopefully displacing any antifreeze that seeped down.