Hi Anthony

If the User has sufficient rights to do so, yes. They can click on the Person Record Hyperlink and once the Person Record opens up, they can click change and edit the fields required and the change will reflect back to the Opportunity.

You can also do the change via the Person Record directly.

I think the question is "When looking at an opportunity, can you change what is shown under the company / person fields - currently it displays the Business Phone Numbers"

Avolpe - the anwser I believe is 'no' you're unable to change this core functionaity. 

This is additional information is really part of the core behaviour.  It is possible to override it but you would just make a problem for yourself with upgrading and testing.  BUT you can add additional information.  You could add a field to this block that displayed any information you want using the client side API.  The API can make RESTful calls CRM to fetch additional information.