Jobs, logins, linked servers, server side DDL triggers, logon triggers, SSIS packages, database mail etc etc will all be lost.

I have attached a powershell script which will export all SSIS packages from MSDB to file system.

Take a look at SP_REVLOGIN, to script out logins.

The rest would need to be scripted or documented so that it can be re-created.

If you can and you have spare hardware, do this side by side as its a big task to do, that way you also have a quick rollback method should it all go wrong.