refinishing stairs, kind of

Okay, I'm doing a job for my mother-in-law. She wants the railings on her stairs and the side of the treads that is wood to be a dark brown or black. Currently it is just wood with some type of clear semi-gloss finish.

What is the best way to handle this? The easiest method for me to do this, if it were possible is to just apply a dark glaze to change the colour, though I know this is not the ideal way as far as looks would go, it would make my life a lot easier.

Otherwise, to remove the current finish what methods do you guys find most efficient, as I've always just sanded down and refinished anything I've ever needed to do.

Sanding? (would pretty much take months unless I ripped out all of the balusters, which I would rather not do)

Chemicals?

I'm just doing it while I'm here to do some other projects, and it would not get done unless I do it for her.