You can use DVDshrink to split the DVD into 2 disk. In Re-author mode, just drag your main movie title over. Then use the START / END feature to split the disk. So in other words, Set the END to the middle of the moive or at whatever point you want to have the fist disk end. Then click backup.
Then creat a new reauthor window and do the last part of the moive with the start /end feature. Then burn each part in Nero. I there there is a guide on dvdshrink.info that tells you step by step.