Coolant in oil

So this is big error on my part to begin with. I was trying to fix a friend's check engine light and one of the trouble codes had mentioned that the camshaft position sensor synchronizer was potentially one of the issues. So I thought no big deal, it's not that invasive to get to in should be an easy fix, right? Well in my grand wisdom I just pulled the sucker right out. Without marking anything. So needless to say I was trying to figure out the timing and the position of the position sensor synchronizer and somewhere along the way after a couple of different tries see engine started sounding like Chitty Chitty Bang Bang upon starting it. And shortly thereafter while I was staring at the engine I could hear some liquid being poured into another liquid within the engine. It wasn't until later when I check the oil before starting it again that I noticed the oil level was very very high and that it was milky. Obviously water and oil so I was thinking maybe the head gasket failure due to the very incorrect timing? This is not my car and I'm feeling like a bit of a dummy for my blunder and trying to fix it promptly to make it right. Also follow-up question what's the easiest way to find top dead center when there's no timing marks on the crankshaft pulley so that I can actually try to get this timing correct after I fix whatever the hell I screwed up on this engine. I want to thank any and all people, in advance, for any helpful advice given and for your time used to answer my question/emergency.