Hello Neh,
You should be able to replace the logo with ease by using the native feature in IPB called "Easy Logo Changer". From the ACP, go to Look & Feel and under the sub-menu labeled Look & Feel you should see Easy Logo Changer. Once you have opened the tool, change where it says Apply to which skin set? to your skin name and enter the URL into the field below. Once your information is set, press Submit.