Drain all the oil you can, empty the filter too. Refill, drive it around, lift and tilt, dump that oil too. You will need to keep doing this till the system is clean, then replace the main filter.
I believe you can get filters that absorb small amounts of water. You will need to drain it and flush a few times with fresh oil. You need to get the fresh oil everywhere though, drive it around, lift/tilt to get the oil in the rams. It just needs to be well mixed.
Good luck
