If you go to Walmart, you can get a nice multipack of fuses along with a fuse puller for less than 5 dollars. Cheaper than what I found at a regular parts store, somewhat surprisingly…
I do look around. Believe me, I don’t see many 15-20 year-old cars on the road. When I do I really admire them and their owners. I don’t believe in the planned obsolescence economy.
E.G. If a microwave oven can last for 20 years and safely work that long, keep it for 20 years.
Agree that you need a new thermostat, that is not a fuse problem. Now for the CD. First, do you still have the factory radio in it or is it aftermarket also. Most aftermarket radios (aka head units) put out more power than the factory head units. Also, I don’t know if it is possible to connect an old trunk mounted CD changer to a modern factory head unit unless you really know your audio electronics.
To remove the CD changer, the wires will need to be disconnected at the head unit first. If you have an after market head unit, chances are that it will overload your factory speakers and that could be why you are having trouble with your speakers. Did you adjust the fade control to see if the rear speakers are just turned off?
As a general rule, if you have an after market head unit, you will need to upgrade your speakers. Even the $40/pair speakers at WalMart will usually handle the power of after market head units as long as you haven’t added power amps. For good sound, two pairs of good quality after market speakers will be needed. I like the Polk Audio at about $100/pair as the best bang for the buck, some others here will not agree with me though and have different recommendations.