RAM in a MBP makes no difference to video performance because it has a dedicated card. In the Mac mini and the MacBook, adding RAM won't make the video abilities any better - it gets 64MB regardless - but it makes using the system smoother and easier because that 64MB taken up by the GMA950 makes less of a difference with 1GB or 2GB than it does with 512MB.
Adding a second external monitor to a MacBook Pro (or any Mac outside the Mac Pro) is not supported and shouldn't be considered as an option. If you need the room, get a 30"ACD - it will work perfectly on a MacBook Pro.