How to manually manage apps

Well, i have an ipod touch 4g, and my ipod is formatted for a PC.
my friends birthday just passed, and he got $100 worth of iTunes, and he plans to spend a big portion of that on apps.
he has a mac.
i have 315 apps on my iPod Touch. yes i know i have alot.
i also manually manage my ipod touch so i can get movies from him and songs from my brothers mac without having to move them to my pc
so if i plug my ipod touch into my friends mac, and then click sync, will i get his apps, keep my apps, and not add any music or videos?

i dont want to test and try because it take like 2-4 hours to resync all apps, and then extra to reorganize them.
(somebody chnged my password once when i wasnt looking which is why i know that)

 

how does he change his itunes to manual also?