USD tends to have better exchange rate in Korea but since lately RM to USD is quite high    so i don't think is a good idea. you won't pay using USD unless at the airport duty free

going there by free and easy method? does your RM4k including accommodation? it will be sufficient just for foods and moving around for 2 pax (excluding buying stuffs) but that is depends on what kind of transportation method you using and the food you eat 

no rush but it depends on whether do you feel 3 days is enough for you to spend in Seoul or not hehe..

I will be in Korea for skiing. Early Dec, snow is usually manmade. You don't need three days in Jisan. Jisan can be done with day trip as it is about 40 mins away from Seoul.  You can designate one day for skiing. Not rush at all.

The price does not include ski clothes which you need as without it you will get cold and wet.  So that is an additional 20,000 won per person or 40,000 won for 2 pax.  Total is 290,000 won. Plus food for the day (estimated at 100,000 won) then it comes to about 390,000 won. Is it an overnight trip? It does not include accomodation right? Its quite expensive.

Please note that Yongpyong is 2 1/2 to 3 hours away from Seoul so if you take the tour and leave at 8 you will reach at 11am. There you will probably have about 2-3 hours to ski only and they will take you to the Ginseng place after lunch and then you will have to head back to Seoul.

If you go on your own:-

Subway from a Seoul station to Gabyeon Station for 2 - 2,300 won
Bus from Dong Seoul Bus Terminal (opposite the Gabyeon Station) for 2 - 28,000 won
Rental of Ski Equipment and Clothes for 2 with a discount coupon  (you can get discount coupon from Plaza Korea in Menara Hap Seng or download online) - approx 60,000 won.
Return Trip Taxi to Yongpyong Resort - 16,000 won or you can take free shuttle from Hwenggye
Food for the day  for 2 - 100,000 won
Same way return trip to Seoul by bus and subway for 2 - 30,300 won

The last bus is at around 8 pm from Hwenggye so you can spend at least 5 hours skiing and see other things and no need to go to Ginseng Centre.

Total - 236,600 won

You can save approx 150,000 won which is about RM480

where do you stay? jeju-si or seogwipo area? how come day 2 oredi check out from hotel? you no need overnight on day 2 since day 3 you still in jeju? 

the attraction i listed below on your Day 1 is at Seogwipo area. do you know you need to travel all the way there and back to Jeju-si?
O’sulloc green tea
Mount’ Sanbang
Cheonjeyeon Waterfall
Dinner (Black Pork Street )

on Day 2. do you plan to view sunrise from Seongsan Illchulbong? if yes, you need to go there first

on Day 3. you plan to hike mt halla during winter time? Yeongsil - Nambyeok Bungijeom trail estimate around 3hrs each way and it's better to check the hiking time as time differ during winter season

ahh.. ic.. if like this than your itinerary no issue.. can go ahead 

but for this below. i guess you visit folk village first before heading to check in your hotel. as it's on the way to seogwipo after your visit to seopjikoji.
Lunch & Check In hotel
Seongeup Folk Village
Jeongbang Waterfall

Back from Seoul + Jeju ......overall good trip but weather was really too cold for me. Went for ski at Yongpyong resort, recommended!! the kids were very cool when they ski pass through me as I'm still newbies and fell few times, butt pains like hell.

When to when you at Seoul .. ? Snowing or not when you are there ... ? Weather really so cold .. ? Me going next week 6th - 13th Jan ... but saw weather forecast this few day no snow ... so sad

I plan to go Jisan skii .. not sure as good as Yongpyong or not ... !!!! Any nice place introduce since you just back from there. Thanks

But Yongpyeong i know Dragon peak most of the time is snowing. May i know how you go to Yongpyeong and how much the cable car up to Dragon peak? Thanks