Are there Get/Set methods for addressing commerce line_items and order object properties? Are there get/set functions/methods for all line item and order properties?

I find myself manipulating line items thus:

$line_item-&gt;commerce_unit_price['und'][0]['currency_code'] = $whatever;


I was thinking there must be a better way to (ie. without addressing array members?) My concern is that the structure may change as Commerce develops.
What you're doing is correct for Commerce 1.x.  Drupal 7 just uses stdClass objects for entities, no methods. Fortunately Commerce 1.x isn't seeing any significant changes - any time we make an API change it will be heavily noted in the change log of a new release. Additionally, Commerce 2.x on Drupal 8 is actually able to use robust classes for entities, so the future is brighter.