It should be obvious but spend a couple of days getting used to XC skis before heading out with a pack. Don't take a "heavy pack". It's amazing what some people lug with them, even pots and frying pans dangling off the back of the pack. Travel super light - but not to the point of camping in a bivvy bag, also potentially lethal. Make camp, dump the pack and go have some fun.
It also helps if you go with someone who knows what they are doing. I started the XC ski school at Charlottes Pass 35 years ago. I took hundred of beginners onto the main range (not all at once ;-) ) and had many doing rough teles on the first day. The hardest thing for downhillers to get used to is the freedom of lightweight gear, for example the ease of doing step turns in difficult situations.