I've done it, you may want to think about it some more.
1. 500mW is useless. Mine is 3.5W and even that struggles to do anything more than cut paper.
2. Do you have air blast? Because once you get anything useful on there (power wise) it's going to need cooling. And a mechanism for blowing the smoke away from the lens. Lenses hate smoke. Laser modules hate getting hot.
3. Do some reading on the 808nm side of it. Different wavelengths work better for different materials, jobs etc. Mine is a 440nM (blue) laser, but there are all kinds of flavours.
4. The one you linked has no power control. If nothing else, being able to run 1% power just to throw a dot down for alignment then 100% for cut/engrave makes a huge difference.
5. The YongNuo USB breakout supplied with the OmioCNC does not support the M10, M11 commands for dwell free laser on/off. You end up having the machine move to the end of a line, then stop - burning out a huge hole - before the laser turns off. Or switching the laser on at the start and dwelling before it begins the move. Either way, it's horrible. I fixed it by giving the YongNuo board the old heave-ho and replacing it with a UC400Eth ethernet board, which is a whole other project.
6. You'll need to sort out some kind of fume extraction. Most of the things low power lasers can put a dent in (plastics etc) release some fairly evil chemistry when you burn 'em. So you need to rig up an extractor fan and either a shoe or an enclosure for your machine.
7. Safety - make sure you have the appropriate glasses, but also make sure you control access to the machine area. Don't want to blind your cat as he walks through, or your missus as she brings a snack down to the shed for you
So yes, you can do it. It's an adventure. Consider, too, the other option: there are fairly cheap solid state laser units available on their own gantry machines ready to go, probably costing less than what you'll end up burning through in time, materials etc getting it working on the OmioCNC.