Yes, this one was a little bit of a hassle with respect to the search criteria that you have to specify to get the answer that you are looking for.
Unfortunately this is the best that I can do for now. I think that this should get you in the right direction.
I assume that you have a Test Server to experiment with?
I'm researching something at the moment and sort of have my hands tied. SOrry I could not be of more help to you at this time.
FAQ: Switching between SQL Server 2008 editions
There is an extra step that you need to take when upgrading from one edition of SQL Server 2008 to another, for example when upgrading from Express to Express with Tools. This extra step is called Edition Upgrade (sometimes SKU Upgrade) and the net result is that you have to run the install wizard twice when upgrading an existing instance to a different edition
Edition Upgrade is really just another trip through the install wizard in which you provide the Product Key for the new edition.http://blogs.msdn.com/sqlexpress/archive/2008/08/24/faq-switching-between-sql-server-2008-edtions.aspx
Version and Edition Upgrades
Upgrade from Supported upgrade path
SQL Server 2008 Workgroup 1 SQL Server 2008 Standard
SQL Server 2008 Workgroup SQL Server 2008 Enterprise
1 This SQL Server edition can be upgraded to SQL Server 2008 on the 32-bit subsystem (WOW64) of a 64-bit server. http://msdn.microsoft.com/en-us/library/ms143393.aspx
For better, quicker answers on T-SQL questions, click on the following... http://www.sqlservercentral.com/articles/Best+Practices/61537/
For better answers on performance questions, click on the following... http://www.sqlservercentral.com/articles/SQLServerCentral/66909/