HI, you can take KAL limousine airport bus No. 6103 at bus stop 10B at Incheon Airport. The fare is W15,000 which you buy at the counter. Just alight at City Terminal final stop. Do not get off at Samseong station stop. Walking distance to Oakwood is 10mins . you cant miss it.
Take 6013 airport bus direct nonstop to CALT which is just next to the hotel.
Get an answer from Oakwood Premier Coex Center staff and past guests.