Without a battery, you have only 1/500s no matter what mode it's in. Although it's not the worst thing for some Sunny f/16 action with ISO 400 film
I would also highly recommend a disassembly and cleaning of the viewfinder windows and parallax mirror. Matt Denton's site has a good DIY, if I remember right. It really makes a night and day difference.
If you want to replace the dented front ring, you'd need the whole optical group, I think, since it unscrews as one piece.
Edit: I also recommend disassembly not only for cleaning, but the first copy I had came with 2 broken wires connecting to the exposure meter. I would have had to remove the entire rangefinder section to repair them (no thanks on a $15 cam! It was an extremely clean cam so I passed it on). They were painfully visible once the top cover was removed.
Current one...no broken wires and I have a clear viewfinder. It's true what they say...when clean, they're amazing!