Red screen after change display

When you connect to an external display, do you get a normal picture and does everything work properly? If so, the problem is definitely with the display on your Surface and there is nothing wrong with your GPU. Just put a new screen on there, and, if done properly, unlike last time, then it should work fine. If you want to do it yourself (if you want something done right, you do it yourself), here is a guide to replace your screen. If the external display is red like the tablet or some other random nonsense, then your GPU is faulty. If that's the case, then you would have to buy a new motherboard, as the CPU/GPU is soldered onto the motherboard. At that point, I would just consider replacing the whole thing and selling it for parts on eBay.