Paul, about 3 years ago there was a really great article in The Family Handyman magazine about refinishing floors. The value of a source like that is that a lot of information can be offered in an understandable manner and there are pictures that are worth much more than a thousand words. I really suggest that you check out a source like that.
There is a lot of good information that you can access using the search feature of this site also. Questions about gaps between boards, for instance, have been answered many times. I'm not trying to avoid your questions but rather point you toward great information source that already exist.
Henry in MI
PS--Those gaps will probably be gone during the summer. Filling them now actually causes more problems.