Hire a professional....it would be the easiest...
if you wanted to get rid of the black holes, you would have to drill them out. buy putty at lowes or some place and while you are there buy poly. If your steps are stained then you would have to sand them down and then reapply stain, or just go natural...and dont forget to scrape between the spindles...if you have any. dont do the one step stain and finish stuff...its trash.
But most importantly! Only a professional will give you a professional job(in most cases).
As for the risers, just paint them the same as your trim. atleast thats what I would do