Yes do it outside. Drill carefully into the air cell end first. More below.
Just be sure ... I'm sure you're probably right since it's smelling and not wiggling anymore, mine (the live ones) did both continue kicking reliably. I now have another 3 eggs at day 38 who have been kicking every day since 30.
But do bear in mind mine hatched at day 52 and 54.
I had to drill 4 eggs (they were from a pair who weren't mating properly), in my first emu incubation, it was slightly hair raising the first time (Will it explode? Is it really dead? etc).
As it turns out they all went perfectly well. There was no pressure on any of them, even though two were a bit smelly and one was weeping.
However, pressure is definitely possible, although I would guess you won't have any as it is quite recently dead. So do it outside, and point the end you're drilling away from you.
I put the egg in a cup with the bubble end out, lay it down on the lawn, and used the dremel with a carving bit to slowly drill into the air cell. Then I used the same bit working it around to enlarge the hole to about 7mm. At this point I could shine a very bright torch in (Sorry, down under language there, I believe the term Flashlight may be more helpful to you than Torch in the US) and confirm that it was clearly rotten.
It was also obvious from smelling the hole. A late term chick may be harder to determine. If perchance I had found a live chick I would have put a small circle of tape back over the hole and left it.
However as mine were all obviously rotten, I proceeded to drill another, smaller hole in the other end, pierce through with a knitting needle, and blow it out. That would be hard with a say day 45 fetus though. Washing it out and scraping out the membranes was a bit tricky but now I have 4 perfect hollow shells for carving/etching.
Is it the only egg you had or have you more to hatch??