Have some damage on the door, frame, and trim of a few doors due to a wheelchair, what is the best way to fix these? I'm fairly competent with sanding, staining, and finishing wood, but have not dealt with wood that is already stained.
I agree with Jay and fixing the scratches across the grain is going to be difficult to completely hide or fix. It looks like a hollow core door, an unfinished hollow core door slab is pretty inexpensive, I see HD has them starting at $29.
The thin door veneer will make it difficult to sand those marks from the surface. Either wood filler, prime and paint the doors or replace. They are not expensive to replace but are time consuming to cut to length and drill a hole for the lock set.
That's exactly what I would. SS kick plate the width of the door and up to at least 24" from the bottom of the door or higher. The frame I would sand and restain.