Did the engine ruin because of freezing?? No anti freeze during winter!

My next door neighbor has a 1995 Mercury Marquis with a 4.6 engine and it ran good before he forgot about it being run with only water in the cooling system during the winter. It now has water in the oil and I am wondering if the freeze plugs would pop out before something else would actually break in the engine. I know there are freeze plugs in the front of the engine that could let water get into the timing chain covers and down to the oil pan and this could be the source of the water but what would be the other things to check at this point?? How difficult is it to check these front freeze plugs?? Thanks