Lenovo Yoga 2 128GB SSD/8GB RAM vs 256GB SSD/4GB RAM

It depends on your use.If you dont do that much gaming or heavy multitasking then go for 4gb.
While if you dont need that much space at all then go for 8gb ram.
 
Question - I have a Yoga 2 Pro with 4 gb ram. I understand that the ram is soldered onto the motherboard, so that upgrading the amount of ram is not possible. My questions is, is it possible to remove and replace the motherboard entirely? So if I could get my hands on an 8 gb ram motherboard (not sure if this can even be purchased separately), can I remove my current motherboard and replace with the new one?