I have a DS1102E which I've never opened. However, I have been inside my Insteks to look around. Having repaired a Tek 465 and a Dumont 1060 the thing that struck me was how easy it was to sort out the circuitry when it's all on a single board. It's much harder with multiple boards stacked on top of each other. In fact, it seems to me that you could probably extract a schematic using photographs and a bit of AI. An emitter follower shouldn't be that hard to recognize.
It may not be repairable economically, but there is certainly nothing to be lost if you are cautious. Of course, you *will* need another scope if it's anything more difficult than the PSU. I'd buy a new scope and treat this one as a repair project when I felt like messing with it. Or sell it to DC1MC who is looking for a dead unit for parts.