Some people think they know more than they do. People want to help and will try to help even when they do not know what they are doing. The major computer companies have authorized dealers in China, so if you have a real hardware problem, you can contact the company. It could mean that a local representative will have to send your computer to the one place in China where they do repairs. You can buy all manner of computer accessories in major Chinese cities - mouse, printer, scanner, connecting cables, surge protectors, etc.
Major brands are available.
I think these should be okay to buy in China as long as you get it in the box and are reasonably sure it is not a fake imitation. I have replaced printer cartridges and mouse with no trouble. I have not had any problem recently with the power, but in the past when there were power shortages, my computer would run, but the printer would not. This might be a more common problem in smaller cities and more remote locations. Just wait until your lights stop dimming and resume their normal brightness.