A good likelihood is dust build up inside laptop causing a heat issue. If it is 15-20 months old and never cleaned, you might check out the 'how-to' videos on YouTube. The ribbon connectors are tricky - so be sure you know how they work before you try to open them (some slide, some snap, a few lift - DO NOT lift a slider, etc). The screws can get mixed up really easily - so I use cardboard - where I make notes and punch little holes and hold the screws until I need them (really bad to put a long screw in a short screw place, so be careful). Tools have to be the right size, so make sure you have the right ones before you start. I use a variety of plastic ones that I customized from credit cards and plastic spoons - important to keep from scratching things up on the case. A folded towel can help with that too.
I wonder if your wifi card or your router are going on the fritz. If other computers have no wifi problem, then cheapest to test is wifi at laptop - try any of the dongle wifi cards ($3-5) or go for a replacement card ($10-15), route your network through that instead of the current wifi card inside your laptop just to see if the problem gets better.
Also, there may be a Computer Arts class or a Computer and Robotics club at your school where you might find some helpful folks. My first 'super-geek' friend helped me through my first expansion (one whole megabyte of RAM on an expansion card) and then my first couple of builds (feels like 50 years ago...uh, almost is).