Redmine

I have a very old installation of Redmine 0.8.3 that's been in production at my company for nearly 2 years.

I believe that it's time to move to 1.1.x, and I'd prefer to do it using Bitnami. How do I move the DB data, code customizations, email setting, DB settings, etc., from a non-Bitnami installation of 0.8.3 to a Bitnami installation of 1.1.x?

Should I expect any major DB schema changes between the two? Since I have close to 300 people dependent on this, I can't afford an extended downtime for R&D, debugging and solving upgrade problems.

Thanks in advance.
Kunal