2 networks at once (i need help!)

i'm sorry to bother but i need some help...this is a little (maybe even a LOT) over my head. what i am trying to accomplish is to connect my PC to 2 networks at once. i've done a little research online and i read that it should be possible to do this as long as one is wired and the other wireless. Currently i have 2 internet lines in my house. one is in the computer room...on this network i have my wife's PC, my PC, and our laptop, plus our Ipad's and any other wireless junk that we have floating around. There is a hard (read wired) connection from this router to my PC, the machine that i want to join to the other network. I want to keep this as my network for accessing the internet. Our other network is in the living room and has the Wii, PS3, XBOX 360, and DirecTV server connected to it, all wired directly into another wireless capable router. What i want to do is enable file sharing between my PC (on one network) and the PS3 (on the other network) wirelessly. I am terrified of screwing up my existing connection. Would any kind soul be kind enough to help me? i need very detailed specific instruction...

thanks in advance

I just wanted to know if your pc is having the WiFi feature, i mean if it is having WiFi then you can do file sharing within the home network but then it wont be possible to share file from one network(internet) to other network(over WiFi) hope that helps.