On 2011 and earlier Macs with EFI locks: with the power off, remove a ram module and then turn on the MacBook. Immediately hold Command+Option+P+R to reset the PRAM. Reset the PRAM twice. Then once it chimes, the password should go away. It’s a stupid bypass but it works. After the password goes away, turn off the Mac again and reinsert the ram and reset the PRAM again to include the new ram in the PRAM config.
Laptop screen blink could be bad Hall effect sensor all the way to bad LCD cable or backlight power supply. Haier are not known for quality anything, so I am not sure why anyone is buying these things, but ok. :)
PCV valves are usually really simple across all vehicles. They just pop out usually from the valve cover and detach from the pcv hose, and just pop another one in. Do not forget to take a bit of engine oil and lube the pcv o-ring before trying to reseat the new one or you will damage the o-ring.