So last year I re-purposed the force.com labs app Sales Quotes with Line Items to be an Orders app.  This allowed my client to track 'Shipped' orders, as well as 'Projected' orders related to an Opportunity.  This also made it possible to get a more accurate, granular forecast for Sales as well as Production for this manufacturing business.  

I changed the name of the custom objects from Quotes and Quote Lines to Orders and Order Lines.  However, I did not change the API names, which are something like SFDC_255_Quote__c, and SFDC_255_QuoteLines__c because I figured if I did it would mess up the Apex code that makes the Opp Line items bit work.  Its kind of confusing when performing admin functions to have to remember that SFDC_255_Quote__c is really Orders, so I would like to change it, but I'm a little scared.  

How would I approach changing the object API names to more accurately reflect what this object is and does?  Bear in mind I am a complete force.com IDE neophyte, and I know extremely little about Apex.  

Thanks!