It can be a charging problem, I fixed some of this computers, and the fact is that the charging port is secured by small ring of plastic and it does not support heavy use. The charging port (DC Jack ), has a third connection on the center that communicate charger with motherboard, if something happen with that communication you still can see your computer powering on but it never will charge until the computer has a full connection. Well, Just try with a new charging port…
You will need a lot of patience to do it without damaging the screen, but technically you can. Microsoft Surface Pro 6 Teardown It is a hard task, you can damage the screen, there is like a 90% change to damaged it, and is better if you have a Screen ready to be replaced if you damaged. Not even Microsoft can do it, when you call for a repair they just replace the complete device with a refurbished one.
Old phones don’t use Sim Cards they are CDMA network, and they have to be programmed with a new service, I guest your phone is not even supported anymore, you can call Verizon or Sprint to see if they can activate it.
Go to BIOS and check if your charger is being detected , and if not, you have a bad charger or bad charging port, also run Diagnostics on boot F12, the chargers have a small pin on the middle that transfer data, check it some times is bended.
Only if is 100% clean water you can let it dry, anything else will left residual materials that will start making contact between small components inside of your phone. Take it apart and clean it, if the tactic engine still not working, replace it, and if it still not working check the motherboard.
I don’t know your technical skills, but the short answer is creating a new administrator account and now you can change/reset password from your account. There is so many tools on the industry like a flash-drive to unlock your account, or the in the worst case, making a copy of your personal files and reinstalling windows.
Well, there is many of possibilities, not because is new it will work better, for example a computer of 3 Years ago with a core i7 processor will perform better that a brand new computer with a Celeron Processor. Also storage a SDD of 2 years ago will work faster than a brand new HDD 5400RPM. You need a geek talk to resolve all your questions.