That one is entirely up to you.
You can probably resolve it with a basic DMM if there is a problem. Once you’ve got a limping scope you can usually use itself to debug the rest of the problem if there. You tend not to need high voltage probes or anything fancy unless you’ve got a really sticky problem.
I will say that a broken scope is a good classroom.
Before doing anything make sure you can get a good copy of the service manual and schematics however.
Totally agree, it is a good scope, I have the same one in a 50MHz version and is a good performer and it would appear that most of the parts are industry standard ones and as such ought to be available. At least you will be working with a live scope rather than a dead one to start with. Grab a service manual from the Internet, and check first all the supply rails for correct voltages, it is possible that there will be your problem and you may not have to go anywhere near the HT supply.
Looking at the photo it could be as well that the camera had flash on which will wash out the screen traces, and the top trace may also be caught by camera just as the sweep is be blanked. If you have a photo of the controls, check to see the sweep is set in the ALT or Chop mode. If in ALT it will draw CH1 and then CH2, in the CHOP mode it draw both channels together but the traces are going to be noticeably dimmer.
If it's in ALT then it could be just the way the camera captured the scene.