Before you upgrade, you may want to transfer all AutoText to a separate template (.dot file). You can then place that template in Word's startup folder so they are always available. You really should not overload the normal.dot because that can cause corruption.
If you plan to upgrade to Word 2007, you will no longer get the AutoComplete tip box for AutoText entries -- that feature has been removed -- so you may want to consider Word 2003 or using a true text expander. Instant Text can import your AutoText entries.