Hey Veto,
You should have a Merant ODBC driver for Oracle 7 & 8 when you install CF 5.0. The the native drivers are better than the ODBC drivers but I don't think you'll see any performance problems in not using them. Just go under the "odbc" section and you should have options for setting up an Oracle datasource.
Let me know if you have trouble with it,
GJ