I don't really know much about pinnacle, but i know a good bit about editing video in general. There should be some sort of option to set "in & out" points in your timeline, so you can just export the chunks that you want. Let's say you want the first 45 minutes in one chunk. Set the in point at the beginning and the out point at 45 minutes. When you export to AVI, it should only do that much. But then on your next chunk set the in point at 44 minutes so your friend can overlapthe two chunks and line them up. In a perfect world, you could start the 2nd chunk at 45:01 and it would work, but if for some reason it didn't, you would have to do it again.
Again, I'm not exactly sure you can do this with Pinnacle.... hope this helps in some way