Removing skin oils/dirt from unfinished wood

So, a hundred years ago (well, a year and half ago) we had an oak banister installed in our house. Prudent people with one toddler and a baby on the way would have hired someone to stain and seal the thing, but we decided to do it ourselves. So 18 months later, with two small children underfoot, our banister is still unfinished and dirty. Have we ruined our chances of ever staining it or is it possible to sand it enough to remove skin oils that have penetrated the wood? We are worried that if we do sand and stain, old skin oil stains will appear afterwards. Should it be sanded and painted instead? And yes, I’m thinking about hiring someone to do the work; otherwise I’ll be asking this question again when my kids go off to college.

I don’t know what stain you have in mind, but it will probably hide any oils that survive the sanding. Are you going to apply a finish after staining? Something that’s touched that often probably ought to be sealed.

I’m not a pro, nor even a well-informed amatuer. You have been disclaimed.

Thanks AskNott. We’ll definitely be sealing after staining.