The first thing, is its over heating that is why the fans are revving up and shutting down with 2 red lights.
As for the E-74 error your getting this can be fixed just have to try some things first. Try a different av cable that could be causeing the problem.
If that doesn't work then you need to reflow the GPU ,I have had this problem many of times, make sure that you keep the heat even so that the mobo doesnt flex or warp , need to keep the mobo flat and heated even.If the mobo
is warped or not flat you will contuine to keep having the same problem. If warped you need to heat up the board it will flatten back out, but you probably need to get it hotter then the blow dryer or spend more time heating it.
2nd you may have to get some NO-CLEAN liquid flux from e-bay its like $2 to $5 usdollars and this will help when reflowing the gpu or hana chip. make sure you use the artic silver 5 paste also. If you need anything else , let me know I will be glad to help you.
Make sure that when you put it back together. you assemble it correctly and your problems should be fixed.
Follow this guide when you put it back together if your not using the x-clamps
https://acidmods.com/forum/index.php?topic=33083.msg248097;boardseen#new