Sounds like the water seal part of the inlet manifold. Quite common on these cars, new inlet manifold gasket/seal can be purchased from Daewoo parts stockists. Just hope and prey that the manifold itself isn't damaged, engine can stay in place, though you'll find a lack of skin on your knuckles once the job is complete! Once the manifold removed, check for signs of damage on the manifold, you may well find it just needs a new seal/gasket(its a rubber type seal).
You can get hold of the GM TIS(General Motors Technical Information System) on disk from a certain on-line market place whick is as good as, if not better than popular printed workshop manuals which will guide you through the job if u'r not confident with the repair.
Gaz, February 2009