I do not know how long in the snow I wrestled with grisly fear; But the stars came out and they danced about ere again I ventured near;
Our speaker was pretty brave out there on the trail, but now he’s seriously freaked out. The process of burning his friend has really upset him, for obvious reasons.
He stands there for a long time, wrestling with his fear. It’s dark before he can make himself go back toward the boiler where he stuck his friend.
I was sick with dread, but I bravely said: "I'll just take a peep inside. I guess he's cooked, and it's time I looked"; ... then the door I opened wide.
The speaker is determined not to be a coward, so even though he’s "sick with dread," he tells himself it’s time to see if his friend is "cooked" yet.
You know how sometimes when you’re really scared, you make inappropriate jokes to make it seem like you’re OK. That’s what our guy is up to here. Treating his dead friend like a chunk of meat helps him to feel more brave.
By the way, he seems to talk to himself a lot here, doesn’t he?