In case it hasn't already been mentioned, 76c is actually rather cool for a GPU. You can easily run most moddern GPU's at 100c day in and day out with no shortening of life. Lower is always better though and most cards will ofc not be running with a 100c GPU. 76C is fine though.

I'm the same when it comes to sleep, I need it quiet. This is where I find a pair of foam ear plugs really useful. I cover any LED's in black electrical tape after removing some of the stickiness, wind down the GPU fans and pop the ear plugs in. I then can't see or hear a thing after I turn off the monitor.

This isn't a good idea to do if you have children though and need to be able to wake up in (heaven forbid) an emergency. Don't worry about hearing a fire/smoke alarm though, that kind of noise will get through the ear plugs as it's very piercing.