http://poldoc.fem.tu-ilmenau.de/singlef ... e=uoem.xml
Look at the explaination of the flags. For my shard, if a GM+ is placing the house, it will first try placing the house and if it fails, it will display a Yes/No gump if you want to override and force the placement of the house using the flag CRMULTI_IGNORE_ALL.
You wont NEED to make any changes at all that I know of when installing a newer release of UO. They wont change anything either. Since you're built on an older version, think of installing the newer one as adding on to your list of options. You can implement the newer items and monsters a lot easier.