Why do you want to change your MAC address? Generally that kind of stuff doesn't get altered, it's the unique ID of the network interfaces. Only reason I can think of for changing a MAC address is to bypass MAC filtering.
Also which IP address are you referring to? I assume it's not the public IP address allocated by your ISP. If not then it's your private address.
If you want the public one changed then you will have to called your ISP and see what they can do.
If you want to change the private IP then you should set it as a static address on your PC, within the same network as your router. You will also need to exclude the IP address chosen from the DHCP pool of addresses. This is usually done on home routers by 'reserving' an IP address. Check the manual and I'm sure you will find it.
If you need any more help just let us know.