What do you mean by "update my ipod"? A shuffle should not need any software update.
This document shows the four types of shuffles and methods to load content.
http://support.apple.com/kb/ht1719
If it is the current 4th gen (or 3rd gen) shuffle, here's one convenient way to load songs on a shuffle, and maintain its list of songs going forward.
If the iTunes sidebar (along left side of window) is not visible, from the menu bar, underView, select Show Sidebar. When connected, the shuffle appears in the sidebar, under DEVICES. Select the shuffle there. To the right, the shuffle's Summary screen is shown. Toward the top, where it says Summary, click Music to the right of Summary. This Music screen is where you tell iTunes how to sync songs to the shuffle.
Before you set up that Music screen, create a new playlist in your iTunes library, and put all of the songs you want on the shuffle on that playlist. (Or you can use an existing playlist.) Back on the shuffle's Music screen in iTunes, check the checkbox for Sync Music. Choose the option to sync Selected playlists, artists, albums, and genres. Below that, find that playlist under Playlists and select (checkmark) it. You can select other items on those lists if desired.
When you click Apply, the songs in your selection(s) sync to the shuffle. Going forward, to update the shuffle's songs, just update that playlist in your iTunes library (add/remove songs). The shuffle does not need to be connected. The next time you connect the shuffle (or click Sync if already connected), iTunes automatically updates the shuffle with the same changes.
(If your shuffle is the older 1st or 2nd gen model, please post back. It works differently.)