distance from airport

Yes, you can. I would highly suggest contacting a tour company and having them pick you up, take you there, and bring you back. Costs a bit more, but less hassle. I would also suggest going to the Mutianyu gate as it'll be closer (about 32 miles and about 45 minutes to get there). Obviously, the time it takes to get there and the time you'll wait in line to get up to the wall will depend on the time of year and how many tourists are there. You can walk up from the base, ride the cable car, or take a chair lift (about $13 roundtrip).