[calorie]

@Reece^B: Back up your gallery database tables and images directory then follow the instructions in the readme file to upgrade from lite to pro. Don't of course overwrite your images directory!! Set the config file, leave the prefix file as blank, and FTP all the stuff over (except the images directory or it'll overwrite your current one) and then import the XML file allowing overwrite. The upgrade will change the database tables but won't mess with the images themselves.

@smirkley: Good question. I don't have that version installed to test. Last version I played with before 4.2.1 was 4.0.0 and that was before the inclusion of the CKEditor. My guess is that it'll install just fine (you might need to edit the XML file and remove the dependency though).