To fix or not to fix

With the fun I've had with Jolida, IMO fixing anything is just throwing good money after bad.

Take the top off of it and Clean the rubber ring on the spindle that the cd rests on, more often these skips are caused by slipping during playback,over time dust gets on stuff, these disk players spin the discs pretty fast. Also, clean the lazer with a little alcohol and a q tip. Note you may have to remove the cover for the cd transport as well, smaller screws no biggie. POPS could be a bad tube, is it only popping on one side? if so switch the tubes to see if the pop follows to the other channel, if it does you have a bad tube.

Why would the slipping only happen after such a long time?
The sound is from both sides.
I thought it was/is a bad board that only acts up after getting hot.

I have a modded JD 100 that I've had for many years and still
listen to it. I sent it in for repairs about 6 years ago. It
did not cost upwards of $200 to repair though. I would say it
isn't worth it for you to repair, based on the rough estimate
they gave you. I would look to replace it based on your budget
of $500-$700. You may want to try the suggestions for
repairing it yourself, but that's all I'd do.

I'd say when the old CD playing gear finally breaks, its the perfect time to start a computer based music server as a replacement. That's where its all heading. I personally would not invest anything in any high end CD player anymore these days.