iPod touch issue - new apps won't sync

I bought a bunch of apps but had to reinstall my OS, so I lost them in iTunes. They're in my iPod.

I bought Rock Band and one other and when I connect my iPod, they won't sync or appear on my iPod. They'll show up in itunes, but not on my iPod.

Do I have to synch in the itunes screen to get them on my iPod? Doing that would wipe all my old apps.

Yes, you need to sync on the iTunes screen.

Should not wipe any purchased apps at all. Didn't on mine.

In iTunes 8:
If you are checking the box to sync only the selected new apps, then yes, you're telling it to put those two apps on it and remove all the others. You need to leave the 'Sync all apps'
(or something like that) checked.

In iTunes 9:
It should be showing you all the existing apps and the new ones on the Application screen - any of them you uncheck in the left side will be removed. You need to leave everything checked that you want on the iPod/iPhone.

If you haven't upgraded to iTunes 9, it's a worthy upgrade in my book.