Since you have a vertical line, the horizontal deflection circuit (which is responsible for the horizonntal movement of the electron beam across the screen) seems to be defect.
Unfortunately I can't help you repairing that circuit.
If the viewfinder display is indeed a little crt, then repair will be close to fixing a television. (Just a smaller scale)
The problem could be with the deflection coil itself, or the circuit that drives it.
Possible fixes would vary based on the actual fault. Additionally, replacement parts may not be readily available, so it would require someone with the skills to actually carry out the repair. I would be willing to bet the repair cost to have someone fix it for you would exceed a replacement handycam.
I would urge you to not attempt the repair yourself unless you are willing to buy a new recorder. You could very well do more harm than good with a soldering iron inside that thing.