Are you out of the warranty period?
If so, you can try cleaning out the dust, and reapplying thermal paste on the two heatsinks. There are youtube videos showing how to take it apart and put it back together as well as how to clean out the heatsinks/fans/vents and reapply thermal paste. I highly recommend using Noctua NT-H1 thermal paste or similar non-conductive, low thermal point required paste.
If that doesn't work, you might need to re-flow the board/CPU/GPU. If you have never done it before, I would say you might be better off paying a place to do it. You can do it yourself in an oven, but again, it is a little tricky and you need to use the proper temps and length of time, otherwise you risk having components completely detach themselves from the board, or you cause permanent heat damage.
The final possibility is that you need a new power-supply, but the blinking red light is almost always an issue due to heat and/or heat damage that has occurred causing the solder joints to fail.