Car stereo volume decreasing and increasing over time

Ever since i bought my car(1999 Ford Focus mk1), the volume of the standard car stereo(6000cd rds e-o-n) has ben turning itself down and up again over time.

When the stereo has been off for some time, having the volume on 5 will be sufficient. After a while, volume 5 will be too low and i turn it up to 10 to get the same volume as before.
It also has sudden blips where the volume goes back to normal.

it doesn't matter if the engine is on or off

I have a 2008 Ford focus that's running approx. 93,000 miles. Is it worth paying the price for fixing or should I get new car?

I love my Focus but it has had more than a couple issues, but it is ten years old and running higher mileage. I did buy a Focus because they have a reputation for running longer than other cars ( in general comparison).

Recently it deaccelarated while I was driving it. My mechanic asked me to take it to the dealer because my coils were full of oil.so the coils have to be replaced and a cover gasket… Grand total $1,100 to fix. Is it worth fixing or should I get a new car? This is a pretty penny to me.

Prevent car paint from fading?

I have been a car guy for about my entire life but I'm going off to college. I have a brand new 2017 Ford Focus ST in rally red. It is constantly a struggle keeping a red car clean but that's a different story. However, I'm more worried about how to keep my cars paint (especially since it's red) from fading in the sun. So what is the best way to keep my car's paint looking decent while it's sitting in a sunbaked field for most of the time? Keep in mind there's no way for me to move it to the shade or anything like that.
Or has modern spraying techniques become so much better that I don't have to worry about paint fading thanks