If you want to feel comfortable, hire a mountaineering guide to teach you some basics. I also recommend Synnott.

The elevation is not a big deal… but the weather/temperature above treeline can be an issue.

Experience: do you know when you’ll need crampons versus microspikes in various terrain? Do you know what to do/how to navigate in whiteout conditions? Do you factor in windspeed and windchill when looking at weather forecasts? Do you know when an ice axe is necessary, and how to self-arrest? Do you carry an emergency shelter when winter hiking? Goggles? Do you own boots that can take a crampon? Do you know what a rest step is? French technique?

Honestly, some of what I’m saying is overkill (the only times I’ve self-arrested while winter hiking in the Whites have been for fun/practice) but it’s also a good comfort level/knowledge base for beginner mountaineering. You can definitely teach yourself, lots of info online. But it’s also nice to pick the brain of an expert and have someone talk you through various scenarios, if you are willing to spend the money.