Update:
Just used a can of compressed air to clean out the PSU. It wasn't too horribly clogged, but when I shot the air into the fan vent a cloud of dust belched out all over my keyboard. Now I have to clean my keyboard.
The PSU is a bit quieter though. Normally the fan in it was kinda loud but its quieter. I don't know if cleaning the PSU could've effected this, but the PC booted faster as well. At least hopefully the overheating issue is finally fixed now.
I also noticed the PSU was only attached by three screws because the 4th hole won't align with the case.
I didn't get an after pic though, but (most) of the dust is gone now.
As someone that basically has no idea what they're doing, I'm quite proud of myself.