foreigner in Korea applying for a visitor visa to Mainland

I currently live in South Korea, but my work contract is finishing in May and I will be returning to my home in Canada. However, my flight goes to Shen Yang, China, where I will stay for several days before departing from Beijing. I therefore need to apply for a tourist L. Online, however, it says that my Alien Registration Card must have a 6 month validity. Is this information accurate? Since I will be leaving in May, my ARC expires in 2 months. I need to apply, where can I get this done?