Smoke from engine?

So just a little over a week ago, I had a cylinder 4 misfire code. I replaced the spark plug and ignition coil but that did not fix the issue. I had a cylinder compression test done and cylinder 4 had zero. Ultimately, my mechanic determined it was a cracked cylinder head, and he replaced it. Driving my car these last couple days, I noticed a burning smell but didn’t pay it much attention because I didn’t think it came from my car. But this morning, I noticed the same smell but this time smoke coming from the engine. I noticed what looked like a leak coming from the front exhaust manifold, not sure if the valve cover is leaky too. Thoughts?