Question regarding on Visiting HK

Yes, you need to apply for a visitor's type. It takes four to six weeks if you apply for HK Immigration Department. However, you can't apply because you don't have time. I think you may visit Chinese consulate in your area and see if you can apply there. If they accept your application, you will get it in 3 to 4 days. It costs around 30 USD if you apply from Chinese consulate. The required documents are your passport, filled application form affixed with a recent passport photo, connecting air ticket and your green card (both orginal and copy versions).