Substitute for hot Korean chili oil in this pork noodle recipe

Toasted sesame oil is usually the go-to for Korean cuisine. It is included as a seasoning in the last steps of the recipes you link.

Sesame oil is typically used for seasoning, not cooking with. Some types of sesame oil may be appropriate for stir frys and such, but I don't think I've ever used toasted sesame oil (the very strong smelling, flavored one) for that kind of use.

The author of the linked recipe appears to be substituting in turn for gochujang, which in addition to spice has a bit of a yeasty, fermented flavor not unlike miso (no surprise, since both include fermented soybean). Sambal oelek will be brighter, generally hotter, and looser in texture. It's less of a paste than the chili stuff used here, so the resulting sauce will be a bit thinner once mixed and may not adhere to the pork as well.

If it's all you've got, then substitute away! You'll probably still enjoy the end result. However, if you'd like to get a bit closer, here are a couple things you could try, in descending order of effort:

1. Add about 1/2 teaspoon or so of cornstarch to the sauce to thicken and balance the texture of the sambal oelek.
2. Add a small dab of miso paste to the sauce (hard to measure exactly, but I'd say 1/2 to 1 teaspoon depending on your brand of miso). This will have a similar thickening effect and get you a little closer to the flavor of the original gochujang paste.
3. Head to a local asian market and find yourself some gochujang, then substitute for equal quantity for the chili paste in the recipe. Don't worry about having extra, you could use this in a huge range of asian-inspired marinades or other sauces.

As a final aside that has nothing to do with your question, I just noticed that the author of the linked recipe lists one of the last steps as sauteeing the carrots and bean sprouts together. I'd suggest that you definitely not do this to your poor bean sprouts. Go and cook the carrots, or you could cheat and use the coarse side of a box grater to serve them raw with a much nicer texture. That's what I'd do with a dish like this.