I never did the 8.2 to 8.3 upgrade, but I don't think you should have to do anything. Just install 8.3 and go - I don't think there are any changes. To test this, install 8.3 somewhere other than the default or on another machine, change your startup options (.ini, etc) to point to 8.3 instead of 8.2, start the database server, then start your client.
The only time I ever had to do anything to the database was going between major versions - 6 to 7, 7 to 8, 8 to 9. Within the major version, I've never had to do anything other than just install the new version.
Hope that helps!
Rich Uchytil