Can Display Suite render content without my theme around it? I'm just getting familiar with Display Suite and I want to know if I can use it to display only the content - not my header/footer/etc from my theme.  

My goal is to display this content in a modal popup so I don't want anything around it.
aDisplay suite should allow you to modify the output for the fields and even choose some layouts but AFAIK it won't let you completely omit the site theme (i.e. create a page without header or footer).

You can use js/ajax to grab just the portion of the page you want to appear in the modal pop-up so that it doesn't pull in the header/footer. Depending on the JS library(ies) you are using this could be easy or challenging.