You don't need to touch the PHP file for this particular change. You can put the main image code back where it was (under the <!--bof Main Product Image --> ), and move it with CSS.
Separate the selectors so you can change just the main image:
Code:
*Image Display*/
#productMainImage, #reviewsInfoDefaultProductImage, #productReviewsDefaultProductImage, #reviewWriteMainImage {
	margin: 0em 1em 1em 0em ;
	}
becomes
Code:
*Image Display*/
#productMainImage {
	margin: 0em 1em 1em 1em;
	float: right;
	}
#reviewsInfoDefaultProductImage, #productReviewsDefaultProductImage, #reviewWriteMainImage {
	margin: 0em 1em 1em 0em ;
	}
The text will wrap around this if it is longer than the image, so limit the text block width, or else give it a margin to keep it away from the image. (Again, separate the selectors so you can affect only the one you want to.):
Code:
#productDescription {
	/*font-size: 1.2em;*/
	padding: 0em;
	text-align: left;
	width: 25em; /*use whichever works best for your situation - adjust numbers. this will work for a fixed width layout*/
	margin-right: 21em;/*this will work better for a fluid layout*/
	}
/*.content,*/  .shippingEstimatorWrapper {
	/*font-size: 1.2em;*/
	padding: 0em;
	}