Not sure if you can get a tuner module or not. Given that there is no option for it on the screen how would you select it? You might consider an aftermarket head unit that incorporates XM, nav, Apple Car Play/Android Auto and all of the other good stuff. There have bee a couple threads here recently that discuss this.
**EDIT** Just did a little looking. If the headunit is XM/Sirius ready, then yes, you can add a tuner module and probably be done with it. I would assume the antenna is built in to the shark fin. If the headunit is not XM/Sirius ready then you would need to upgrade your headunit. But I didn't find anything saying one way or the other whether it's XM ready or not. On Kia's website, it shows the LXV6 with the XM/Sirius headunit as optional, but XM/Sirius as standard.
Thanks for the reply, Jon. I couldn't find anything either in regards to if it is XM ready or not. I do like the stock unit so it would be disappointing if it is not XM Ready. I'm having someone take a look Tuesday to see what my options are so I'll post what I find out.