I followed their documents, I detached from the SQL express, copied the files over to our SQL server, attached and then had to make one change to the rights or users, otherwise everything made it. So DO check the rights and users and all when done.
You can backup and restore, but in our case, we don't use the default C drive location for SQL data, we use an E drive, so it was easier to place the files where we wanted and attach.
Their document were so easy, even I was able to do it and SQL scares me a bit.
The SQL Express files were HUGE, so our DBA did some tweaking and it went from multiple GIG down to UNDER a gig.