Can I uninstall and reinstall "Pages" without losing files?

You can reinstall the application and you will not lose any of your documents, they are saved as *.pages files when they are saved to your hard drive. Make sure you have either the iWork install DVD or you purchased it from the App Store before you delete it otherwise you will need to purchase it again to install it.

Possibly, however, before you remove it try removing the preference files from the application These can be found in Users/yourname/Library/Preferences or /Library/Preferences. Since the autocorrect uses the dictionary found in Users/yourname/Library/Spelling, you may want to see if the dictionary was corrupted as well. If it is system-wide you should see it in other locations such as Numbers or if you are using Lion you will see it in Safari as well.

If you don't see the preference files also check both /Library/Application Support, and Users/yourname/Library/Application Support.

Yes

Glad I could help