woodworker questions on vintage frames

[mudfud]

hi again

I'm trying to restore this wooden side piece on my sankyo vintage. I think that someone forced the front door open, and split the wood.

questions:

what kind of wood is this? can I find a piece to replace it easily? is this wood expensive? could i substitute something else and stain it?

can I patch it with bondo wood filler (probably unsightly, right?)

how do I get those notches... dado's? on the end??? no router or table saw... have small hand saw and chop saw.

I expect that jeff has ideas, as he's done some beautiful wood work on his vintages.

I don't want to replace the whole frame, just the one piece.

also, when you refinish, when you sand down the whole thing, how do you keep from sanding across grain where the pieces meet? is a clear polyurethane a good cover coating?

thanks for ideas.