A dot in the middle of the screen suggests the deflection coils aren't operating, which could be any number of issues, from power to an input signal problem to the display. The chances are the whole system will need checking over, and probably a lot of capacitors replaced, and with the high voltages involved, I wouldn't recommend you attempt this with little experience. I'd look for someone local who is competent with electronics to go through it, and bring it back to life. I say this, as there's some pretty high voltages (1,000s) kicking about some of those circuits, and it's far from an ideal first project if you are unfamiliar with electronics and safe ways of working with high voltages.
Get someone with experience to help you. In Person.