Hi Nano - I stayed in Seoul and took a shuttle to the ski slope.
This was the site I used to book. Just email them and they will offer you everything.
http://www.winterfriend.com/
I took a package that costs me 105k Won per adult and it consists of return trip on ski bus, rental of ski equipment and full day ski pass
In addition, I also took private lessons.
Here. But prices may have changed. It has been 3 years.
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The whole trip started very early and I only got back into my hotel in Seoul at night around 9 to 10pm.
FYI - The Winter Sonata was shot at YongPyong, but that's a little further away. Heard it is very beautiful but was a little too far out and you may want to stay a night there. I wanted to stay in Seoul and hence chose Daemyung.
Hope this helps.