Applying poly over the paint really won't give you any added protection. It's not like the poly is any more durable than the paint itself unless you are really using some cheap paint.

The first thing you need to determine is what type of finish os on the rail. Shellac strips with denatured alcohol. Lacquer is lacquer thinner. Varnish requires either methylene chloride (fast & somewhat dangerous) or one of the new 'safe' strippers (though they have a real hard time with some varnishes). Stripping interior wodwork during the winter is usually a bad idea. Spinrg, fall, and open windows are a better choice.

Sammy, I'm fairly sure it's oak. I'm not too sure if it's the stringer itself or just some decorative skirtboard. The underneath of the staircase is finished with some drywall so I can't really check to see what's going on under them. I think I'm going to sand it down and give it a coat of stain and see how that feels. I guess I should have done that first! I think the high contrast between the carpet and the trim is bothering me. Minimizing that might work better. I'm not really up for staining all of the spindles, so those will definitely be painted. Maybe I'll go with an off-white on the grey side so that there's a bit less of contrast. Thanks for the feedback everyone!

$3000-$3500 is possibly very reasonable (maybe even low, for 3 stories) depending on your location. From experience, I will say it is very easy to spend that much and get a BAD refinishing job--so bad that you end up painting over it. Choose carefully. I like the walnut accent, but after my experience--I doubt I would risk that much $$ to try to keep it stained.