If you actually, "own the car still" and the insurance didn't keep it, sell it for parts in your local trading post, sell it to a junkyard or buy another one and keep it for parts.
It depends on why it was totaled. If it's cosmetic damage that totaled the car (like a shallow sideswipe) of course. If it's structural, like frame damage, maybe. If it was in a flood, it's probably not a good idea to fix it since quirky electrical problems will haunt the car forever. If it is repaired it would still carry a totaled title but it can be qualified with the brand 'totaled/reconstructed' on the new title.
A car is not totaled in a chapter 13. A car may be totaled while the owner is in a chapter 13. If the car was fully exempted, nothing happens. If you need to buy a new car, you will have to get permission from the bankruptcy court after you file a specific purchase agreement (car loan) which should not seriously affect your plan payments. Why are you not asking your lawyer?