Depending on your computer program, you might be able to export a "privacy gedcom" that will not include those you have marked as private. That is what I do. Also, please don't add unknowns to WikiTree.
I highly encourage you to start with a small set of your 18,000, like around 50 people or so to see how the gedcom upload works. If you can, create a gedcom of one of your smaller family lines and use that as a test run.
There are several steps in a gedcom upload. You upload, a manager checks that it is ok, you look at each potential match and skip those that would create a duplicate or that are unknowns or have no estimated birthdate, you approve the file for the database, a manager checks your matches, and finally, your information is added to the WikiTree database. Then you need to clean up each entry so that it looks good and connects to other relatives correctly. Sometimes it is just easier to type it all in rather than use a Gedcom. http://www.wikitree.com/wiki/GEDCOM_FAQ
We are glad you are here! And we are anxious to see your additions to the WikiTree.
