Hi Socks--
I had a large (5 cm) AN removed in '89, when my daughter was a year old. It took a while to get my energy back (and I subsequently had a nerve graft for facial palsy and tear duct cauterization for persistent dry eye), but overall my health was OK--my balance was decent if not what it was before, and I didn't have a problem with headaches, leaks, etc. It was a very long haul, though, and I was really kind of nervous about how my body would handle being pregnant again, which was a good part of the reason we waited 5 years before having our second child. I was 29 for the first surgery, and 34 when my son was born, and everything was absolutely fine--healthy pregnancy, healthy baby (now a strapping, 6' tall 15 year old!)
I am wondering if you could get your AN doctor's take on this? Your OB-gyn may not have the familiarity with ANs to assess accurately whether your headaches (if they resolved a year and a half ago) are related to the AN or a pregnancy-related issue (as the nausea may also be), and so may be worrying needlessly (and worrying you needlessly in the process!) You say that you've moved, but perhaps you can still get some phone or email advice from your AN surgeon, or get a recommendation on who to see locally for a consult?
Anyway, the most important thing to say is CONGRATS on expecting your first child!
Carrie