Hello, I'm going to toss in a long time local's opinion since I basically grew up there (had a season pass from 2005 until 2013).
As you might already know, Ruka has the best park out of all the resorts in Finland. The kind of a "cult reputation" has only strenghten the park's development and marketing of the resort (for park skiing of course). The park attracts good skiers from all over Finland, Russia and Scandinavia (and apparently from all over the world nowadays). Also, the skiing "highschool" is located there (for racing and freestyle), so quite many good skiers live there. Back in the day, I didn't even realise how good the park actually was until I went to other resorts. If you literally only want to ski park, then you might want to consider, but read the rest.
While the park is great, other types of skiing are kind of lacking for the most part (from a general freestyle skiers point of view). Powder days are pretty rare, and off-piste skiing is quite lacking if we compare to the usual "whistlers/alps/whatevers". The conditions are pretty cold and icy for most of the season. Still, skiing pow is very fun at best. But remember, it's a pretty small resort really, so all the best powder skiing spots are going to be scoured in a couple of hours after opening.
Ruka is mostly a FAMILY ski resort, judging by their marketing. The groomed slopes are taken care of very well. There are many slopes that vary in difficulty, but most of them are pretty short (longest slope is 1300 meters in lenght though). There are loads of family activities to do in the village, including husky riding, cross-country skiing, snowmobiling, ice-fishing, bowling etc etc. The main town of Kuusamo is like any other small town with the basic services. If you want to have constant action, the area is not for you, trust me I lived there for 20 years lol, the main city is basically dead. You could draw a 200 km radius circle around Ruka and not have any "bigger cities" inside of it. But it might be enough for you, who knows. During certain times of the year (opening day, new years eve, Ruka Spring Break) the resort has wild action and parties though, so check those out.
The Finns speak english pretty well, as you would expect from a well educated country in general. Language barrier shouldn't be a problem for the most part.
I have never worked at a ski resort (I assume that's what where you're implying you'd work in), but you can try applying to some open vacancies around the shops, rentals, restaurants or whatever. Can't really help you with the work question.
I am not sure of the accomodation situation there, but you can prolly get a fairly cheap rental apartment from the main town, or the resort area somewhere.
If you are looking to be a "ski bum" who works nights and skis days, I'm not sure if it's worth it. The opportunities are not too special compared to the bigger mountains. Still, Ruka is a great resort and very popular. Ruka also has one of the longest ski seasons out of all EUROPEAN resorts (if you don't count the ones that do summer skiing (actually Ruka used to have that too, but not anymore)). So suite for yourself, do your research, and even if you decide not to pick Ruka, I'd hope you visit there one day for a week or something. It's a great place :)