If you are staying in a cabin, there is high speed internet in your cabin that you can connect to for $9.95 for 24 hours.
If you are at a campsite, you can go to the desk and check out a cable modem internet kit ($175 deposit charged to your credit card, refunded when you return it), then you can connect that to the cable line at your campsite and get on internet for $9.95 for 24 hours.
There are also a couple of wireless hotspots at the Fort. (Meadows trading post and Settlement Trading Post), where you can connect for around $5 for an hour or $9.95 for 24 hours.
There is also a computer center in the little building above the checkin lanes where you can connect with a traditional telephone modem (check your internet provider for local call in numbers), or they have a high speed connection in that room. The same fees apply.