Visa processing agencies

Hello,

I am from the United States but living in Krakow now so I have a Karta Pobytu/ Polish residence card. I want to apply for a tourist visa for China for three weeks vacation. I will be visiting two friends and planning to stay at their apartment. What do I need to submit then, as I won't have a hotel reservation? Also, are there in Poland agencies that I can pay (for example a travel agency) in Krakow to go and apply for the visa for me so that I don't need to come to Warsaw twice? Thanks,