How to test individual pieces of hardware

So I have my laptop in pieces now after a liquid spill (bought a new keyboard and cleaned the logic board of corrosion) and I'm wondering how I can figure out which, if any, components are damaged. After the spill I was not able to get back into the computer normally (my usual administrator password was not working despite using an external keyboard to type it, password hint same as always). So I'm wondering if maybe the hard drive is damaged? Should I just put the whole thing back together and see what happens? I saw somewhere that you should put in one element at a time and test those somehow but I can't find any more information. I'm very new to this so any help would be appreciated.