Manually manage the videos on my ipod?

I've set my ipod on manually manage because I have over 3000 songs from 3 different computers (including this one). Now on my laptop I bought 2 seasons of a show and halfway through the second season I bought a new laptop and gave the old one away. I was able to get on itunes and started redownloading those eps but when I try to manually put the shows on my ipod it says it wants to delete the eps on my ipod. How do I get past that?