The iOS version is not updated automatically, though if he connects it to his computer's iTunes (if it's a recent enough version) he should be prompted as to whether he wants to update.
He should connect the iPad to his computer's iTunes and copy any purchases off the iPad to his computer via File > Transfer Purchases. He may also want to copy photos and any important documents off the iPad as well e.g. via the file sharing section at the bottom of the device's apps tab when connected to iTunes, via wifi, email, dropbox etc - they should be included in the backup, but it's best to have a copy of them outside of the backup just in case. He can then force a backup of the iPad by right-clicking the iPad 'Device' on the left-hand side of iTunes and selecting 'Backup'.
He can then start the update by selecting the iPad on the left-hand side of iTunes, and on the Summary tab on the right-hand side clicking the Check For Updates button
Updating to iOS 5+ : http://support.apple.com/kb/HT4972
His iPad should update to iOS 5.1.1 (which is the only version that is 'signed' by Apple for the iPad 1, it doesn't support iOS 6).
Latest version of iOS that the original iPad can run is 5.1.1
He can connect his iPad to the computer that he normally syncs
with, open iTunes, and click on the button for 'Check for Updates'.
Updates do not occur automatically. If he is running a version
of iOs prior to iOS 5, the update can only be done while connected
to a computer using iTunes.
And King_Penguin did a much better explanation above while I was
Message was edited by: imobl last sentence added.
If the iOS on the iPad isn't 5 or higher, the update will need to be completed using iTunes on his syncing computer. Check out the directions in the Apple article below. Please note the highest possible for the 1st generation iPad is iOS 5.1.1.