My advice? Try not to worry too much about it. Accept that you'll have both changed, and that those changes are probably a good thing. You'll both have grown and (hopefully) matured, so there's no need bringing up old issues which probably aren't relevant anymore and are just going to cause unnecessary tension. If you want to (and are making the effort to) see them after however long, chances are they are (or were) someone who was important to you. There was a reason for that. The worst thing that will happen is that you'll go back to not speaking to them, or you won't meet up again. Considering that's been the situation for the past however-many months, chances are it'll be okay.
I know I was almost ill I was so worried about how I'd react when I saw someone who had hurt me, but once we got talking I remembered exactly why we had been best friends for so long. Things weren't back to the way there were, and there was always going to be awkwardness and a bit of a guard up, but afterwards I felt so much better - not only about the person but about the whole situation surrounding them.
Have you had to meet up with someone you haven't seen in ages (friend, family member, ex-significant other)? How did it go? Any advice for someone else? Tweet me @VickiMaitland or leave a comment below.