Flight
Rapid City Regional Airport is around 57 minutes (60 miles) from spearfish. Taxi, shuttle, and rideshare services are available from the airport, but I am not sure if they'll take you all the way to Spearfish. The Airport is served by American Airlines, Delta Airlines, United Airlines, Allegiant Airlines, and Sun Country Airlines.
Hotel
This will be camping. The 8 cabins are very minimal including fitted sheet, blanket, and pillow. The bathroom/showers are not connected to the cabins but are within walking distance. They also have full RV hookups including water, sewer and electricity. Tent camping is also available as well. Visit their website for more details or call the number to reserve a cabin.