Disclaimer: Advice is provided to the best of my knowledge but no implicit or explicit warranties are provided. Since the advisor explicitly encourages testing any and all suggestions on a test non-production environment advisor should not held liable or responsible for any actions taken based on the given advice.
I noticed that using "Linked Server" which connects from the Microsoft end is an easier to setup and use link. However, in this case the link is from the Sql server end and you will be able to query oracle tables there and not vice versa.
I am an Oracle fan, but think about it, why make all this fuss of manual changes in listener/tnsnames and activation of HS (Heterogenous Services) features instead of doing it at the click of a button. My guess is that they should be including this in the latest OEM version in lines similar to the Linked Server in Microsoft.