They started soldering the CPU and GPU on the 17 R2 so you are stuck with what you have unless you want to replace your entire motherboard. You can try The Parts People to see what is available but you're still going to be limited to the 980M at best.
You will be able to upgrade your memory (most likely up to 32gb) but I have no idea about the display sorry. I wouldn't image the 970M being a great combination with a 4k display.
If you're still running a mechanical HDD then switching to an SSD will show the best results for what upgrades you can actually do.