Hi Paula,
Click here for [http://www.wikitree.com/wiki/GEDCOM GEDCOM Help]
I'd encourage you to do a small one for now to get going and then wait until we switch over to our new import process. It'll be a lot easier for you to move your GEDCOM then.
What many of us do is focus on our immediate and direct line ancestors first. See Splitting a GEDCOM here: https://www.wikitree.com/wiki/Splitting_a_GEDCOM