"Why will my Surface 3 not charge, but has the light"に関する回答I think that you may find this guide about Surface 3 charging issues to be very informative. Hope that helps, Harold
"How do I upgrade my ram?"に関する回答In a way, yes. At least if you are actually talking about storage space, not RAM. If you did really mean to ask whether the RAM could be upgraded from the 2GB that your model has, the answer is a definitive "No." For the storage space question: There is a MicroSD expansion slot under the kickstand. As I understand it, you could install a 64GB expansion card in that slot, thus massively increasing your maximum storage capacity. You can learn more about adding an expansion card here.
"Can the Mini DisplayPort socket be replaced?"に関する回答Technically, yes. Realistically, however, you are going to break far more than is worth it trying to get to the part to replace it. The Mini DisplayPort socket is soldered directly onto the motherboard, so if you were to replace it, you would likely need to replace the whole motherboard. (Unless yours is a purely mechanical problem, in which case a new socket could be soldered to the motherboard as a replacement.) The real problem lies with the initial opening of the device, however, as unless you are already experienced in removing this type of screen, you *will* break it while removing it. You also stand a very good chance of mangling your WiFi antennas while you are at it. For most, the Surface 3 is simply not a repairable device. Many of the design decisions made to allow for the extremely light and thin tablet have made it so that opening the device once it has been made is an exercise in frustration. A well equipped repairman with the right tools, skills, and direct experience with Surface 3 repairs...