If you are in Wudang and you're not going to Shanghai anymore I'd suggest you start travelling south west towards Chengdu, Shangri-la, Dali, Kunming, Jun Jinghong, Mengla and then into Laos( Daily bus goes from Mengla to Oudomxay in laos, about 4-5h drive: depends on the weather).
Don't know about visa on arrival here cause I was travelling the other way around and had my Chinese visa ready.
Of course you should know that this is a very long trip and expect to pay a lot for transport in the end so if you are not planning to visit the places I mentioned above I would fly to Kunming and go on from there or just fly straight into Vientiane.
If you can't find direct flights then travel to Xi'an from Wudang(not that far) and catch a flight there. (Again: Only if you are sure you don't want to visit the other places because Dali and Shangri-La are really beautiful).
Shanghai is indeed westernised. It's worth a visit but definitely not too long. It's good for night-life! Maybe now it is good to go there because of the Expo which might be interesting.
Hong Kong is a must do but not for too long. Just to check it out(Hong Kong island, Buddha statue, ...) If you have time and going to Hong Kong I'd suggest you go to Macau as well (casinos to check out but also some nice local Portuguese/Chinese markets).