As far as doing it it's up to you. If you can 3 and feel comfortable on your skis you can do it.
COMMITMENT IS EVERYTHING! The worst falls are people who back out because they're scared. If you decide to do it you need to fucking DO IT. Peoples reaction is to not huck it hard and back out, or to turn to the side, that's how you get hurt. It's weird. The easiest way to get hurt is to be scared of getting hurt and try to get out safely. If you huck the thing legit there is like a %95 percent chance of coming close to landing it. You might even land the first one. It's common for people to overotate the first one. As long as it's not by a ton or on a huge jump that's not bad. Better to fall back than catch your tips.
I recommend being comfortable doing them on diving boards or trampolines first but not necessary. If you haven't done any kind of backflip, find a mellow hill and do a backroll without your skis. Get the feel of rolling backward going directly over head.
Find the right jump. You want something that isn't too big but gives you plenty of height to easily get the flip around. You want something you feel very comfortable on.
Hit the jump a few times and get a feel for the air. Imagine you're doing the backflip. Try to visualize the flip to fill that amount of airtime.
When you do it you're going to ski straight at it. You want to crouch a bit to pop. You want your hand down by your side bent a little and ready to throw. When you nearing the top you want to bend your knees a bit more. Your upper body can come a little more forward and your arms might go a bit more behind your legs.
The pop. The pop is the most important thing. When you throw the backflip, fucking throw it. You want to explode upward and throw your arms directly over your head and bring your knees into your chest. The easiest way to learn is generally to tuck it but whatever feels comfortable.
Just remember to throw straight back. Look over your head for the landing. Don't turn your head to either side look directly behind you like you're doing a back bend or something. Your body will follow your head. If you turn your head you're going to spin crooked. If you pop correctly and look over your head straight you're golden.
On the backflip you can spot the landing in time to tuck harder or open up. On your first one it might feel weird to the point where you're just along for the ride. That's fine. If you feel like you're going to under rotate really bring your knees into your chest and hold them till your tips clear.
If you stomp it first try, awesome you just did your first backflip. If you don't it's all good, you just grew a pair and sent your first one. Figure out if you're under or over rotating and try and adjust your flip to get you landing better. Also look for the landing and try to adjust more in the air.
When you get it down keep doing them. The more you do the more comfortable they'll be until it's second nature.
At that point congrats on learning quite possibly the most fun trick in skiing.
PS: there is now a torch to carry though. When people want to see a backflip you are now compelled to deliver the goods as a card carrying member of the invert society.