Studio xps 1645 motherboard

I have a Studio xps 1645 laptop with a motherboard model number 0Y517R and I need to replace it.  I am finding mixed information about GPU and CPU online.  I have an intel Core i7 720QM clarksfield socket 989 rPGA and my GPU is the ATi Mobility Radeon HD 4670. Is this GPU soldered onto the mainboard or is it interchangeable and I am having trouble finding this model number anywhere.  I am seeing 0Y507R but not this one. Any input would be very helpful.