Hello I will help you with your question,
Yes you can remove the adapter and replace the O ring and the gasket behind it. This should stop the leak as it is fairly common for these gaskets to fail.
Nothing but oil will come out when you remove the adapter it is just a messy job.
Remove the two bolts and then you can remove the cooler.
This job calls for .6 hours but plan on twice that for all the grease involved.
Let me know what I can do to help you with this