unless you're familiar with Java Software Foundation you should take a developer to do this
we imported over 7 000 000 documents ( and +1 000 000 spaces ) with metadata ( with multivalues ) and security on space and document level in as little as 10 days and are importing every montch more than 100 000 documents and spaces
it is custom developped based on the space requirements where a document should be placed but it was developped and tested in less than 10 days and deliverd as an amp file
it's a pitty that such a feature has to be redevelopped again and again ( Filenet & Documentum have them standard on board ! )