Functions of factory h3t radio
 

I have a 2009 h3t base model. The other day the speakers on the right side of the vehicle quit working. All I have on that side that is working is the a-pillar tweeter. I also noticed later that evening also that some of the radio button lights quit working. I was planning on replacing the radio with a large touchscreen unit. However, the best buy rep told me I need an interface module thing and another antenna module thing for my serious/xm radio to work. Why would i need another antenna for xm if my vehicle already has one? And what does the other interface module actually do? Any advice would be greatly appreciated. Thanks.

Antenna? dont know why,dont think you need more.
IFyou have monsoon amp in rear there are a lot of wires going back to it to be amplified for all separate speakers. That requires an adapter like gmos 04 which has been discussed here endlessly.
Im not an expert on this,just an interested reader of posts. I did attempt to use a different radio with this setup and gave it up. It was a huge mess of wires, hard to store in the dash!
For me,there is nothing in my experience like monsoon audio in a vehicle.
Just my opinion. If you have monsoon I would fix or replace it with same. Jmo.

U do need another antenna i had the same problem when i bought my 08 h3 base. They ended up changing the deck all the speakers to clarion bits. But also had to replace xm module and new antenna wich came with the xm package all together it was over 700 luckily i just got it and didnt have to pay for it

And my clarion sounds better then the monsoon hands down no offence it sounds decent for a factory system great actually. But you cant beat aftermarket audio. Lol

Where did you mount the new xm antenna?

Pretty much same spot opposite side