Welcome to the Coffeeroom, Aurora! If I were in your position, the first things I would do are 1) join the Orthodox Conversion to Judaism yahoo group, 2) acquire a copy of the Gerus Guide by the group’s moderator Rabbi Aryeh Moshen, and 3) contact your local Orthodox rabbis (including Chabad and non-Chabad) and attend their services. I encourage you to continue your genealogical research (mainly because I love genealogy myself), but keep in mind that you don’t have to be able to prove Jewish ancestry to convert.
I would also read books on Judaism from an Orthodox perspective, as well as websites (such as outreach-oriented sites such as Chabad, Aish, Simpletoremeber, and Breslev Israel). At some point you might be interested in reading the book on converts (gerim) in chassidic thought by Dov ben Avraham (who himself is a convert with some Jewish ancestry).
I agree with yichusdik’s suggestions, with one caveat. From the way he phrases it, it sounds as though abandoning the observance of mitzvos will invalidate the conversion. This would suggest that you can convert, be an Orthodox Jew for a few years, and as soon as you get tired of it you can stop being observant and poof, your conversion is invalidated and you’re no longer obligated in the mitzvos.
It doesn’t work that way. When you convert to Orthodox Judaism (the only real way to convert to Judaism), you make a commitment to be observant for life. If soon after the conversion you are not living a completely observant life, that will be taken as evidence that the conversion was not valid, because you did not accept the mitzvos. That is the only way a conversion can be nullified.