I don't know what to do. It gets super hot and uncomfortable to type. I already can't use it on my lap because I would literally burn my thighs. It also gets super loud (fan) if I try to add a game to the mix and everything starts stuttering till I just shut it down.
some canned air to blow dust out of the vents, a vial of new paste to replace the old stuff, and a new battery sounds good, gonna feel like a whole new device!
while you're already opening up the laptop and disassembling things, if you have the extra cash you could replace the hard disk with an SSD if you felt inclined. (assuming you dont already have an SSD in your laptop)
of course changing disks out comes with its own hassle like re-installing the operating system and am understanding if thats too much to deal with
probably windows will complain but if the SSD is >= old HDD size you can just copy the whole disk and avoid reinstall hassle