. The Tomb is in Mongolia so a long way from the sites mentioned.
Yes the pollution in Beijing can be bad but worth the trip
There is so much to see and a lot will depend on personal tastes. Read as many guides as you can there are some good ones on line. The tour will provide your basic needs and as they are used to Western tastes you will be OK for hotels etc,
Just remember that China is a huge country, population and area, they do things differently there. Be willing to accept large numbers of people everywhere Facilities will be basic in many areas.Ater living there for 6 years I can give you the following advice.
1. Stay away from Chinese toilets – use hotels restaurants etc,
2. Follow up to # 1 watch what you eat and drink. In tourist areas you should be fine but watch out for street foods . They are not dirty as such but the cooking methods can effect your tummy. Some of the food can be very spicy
In Beijing have Beijing Duck, in Shanghai try the sea food particularly the fresh water Shrimp and in Xian the noodles and roast lamb.
3. Tourists are walking ATMs and a lot of people will be out to make money. When shopping in markets bargain and treat it as a game – don't get too uptight about it or you will spoil the fun. You will never get a local price so offer about 20% on the opening prices and hope to settle for a third. Ask your guide if bargaining is OK in many up market shops there are only fixed prices. Your guides will also take you to places where they get a cut so watch the prices but sometimes you can get a deal. Treat all antiques as fakes and pay accordingly. You can buy pirated goods , CDs, DVDs, clothing, etc very easily but a lot of governments could take them away from you if they see them at Customs when you come home and most Chinese electronics DVDs etc will not work in the west
4 Keep your mind open China is changing daily and you are going to see some wonderful things. The availability of luxury western goods, modern buildings contrasted against old Chinese buildings, poverty and a sense of energy and change. Chinese cities make Western ones feel like small towns. Bring a good camera and expect to take three times as many pictures as you think you will
Your tour should show you the basic highlights. so see as many as you can If the weather is warmer street life should pick up go out and roam around yourself when you have the opportunity. Chinese people are generally very friendly and will like you back id f you show you are willing to accept them as is.
Above all go with an open mind and be prepared to have fun