So no water got into your oil?
Keep in mind, water / oil in your block / over your bearings is not good.
I know when my sleeve cracked, the water and oil were seperated and not milky. I had water sitting at the bottom of the sump and oil floating above. The dipstick didn't show signs of water at all.
If there is evidence of water in your oil system and if it has been sitting, you could possibly also have some rust building internally.
Regardless, the gunk is not good as expressed in the above posts.
Have you drained the oil? if not, drain it and see if you have water in the oil. If you have signs of water, pour some cheap stuff in and turn it over and get oil into your galleries and journals. Also, might be a good idea to pull the plugs out and get some wd40 into the cylinders. This will prevent any water (if any) to disperse and stop the cylinder walls / tops of your pistons / rings from starting to rust.
Better safe than sorry!
As for cost, it is quite time consuming so you'll be up for a good days work and the cost of the headgasket + other small parts.
If all is good, might be a good time to get a cometic gasket and some ARP headstuds!
Who's doing the work?