There are plenty of people selling merchandise such as t-shirts and scarves so you can look the part once kick-off happens. However, the city has plenty of great air days, and the situation has improved a lot even in the last few years.
To buy tickets online, simply follow this link. You can also find bicycles for rent if you prefer to move a bit quicker and get some exercise. Mutianyu isn't as easy to access and it is recommended to hire a driver or take a tour. Of course, you can just walk and go at your own pace.
Concerning the difficulty of finding our way in the Chinese capital, our 5years training in the parisian urban jungle gave us all we need to roam in the steets with perfect ease. Be sure to spend time in the park to enjoy some Tai Chi or Chinese yo-yo. Following the success of the Kuomintang 's Northern Expeditionthe capital was formally removed to Nanjing in To be exact: modern and titanic!
A word of warning, however — not all sections of the wall are actually great. That is, a karaoke bar.